overwrite the same field from another position

I have some profile extra fields. I edit them from wp-admin/user-edit.php?

These data are displayed i.e. on all the posts of the same author. But how could I overwrite the same field from the position wp-admin/post-new.php ? Which is the purpose? Imagine that all the apartments (posts) managed from one agency (author) have the same cost for final cleaning, 50 euro. Ok, I can manage it from author/agency level, but if just one apartment has a different cost, i.e 80 euro, I should have the same field at apartment/post level, and this field , which is further downstream, overrides the one which is further upstream. An example of my profile extra fields:

add_action( 'show_user_profile', 'my_show_extra_profile_fields' );
add_action( 'edit_user_profile', 'my_show_extra_profile_fields' );
add_action( "user_new_form",'my_show_extra_profile_fields' );
function my_show_extra_profile_fields( $user ) { ?>
    <h3>Extra profile information</h3>
    <table class="form-table">
        <tr>
            <th><label for="richiesta">Richiesta</label></th>
            <td>
               <textarea id="richiesta" name="richiesta"rows="5" cols="30" class="regular-text" ><?php echo esc_attr( get_the_author_meta( 'richiesta', $user->ID ) ); ?></textarea><br />
                <span class="description">Richiesta del cliente.</span>
            </td>
            <th><label for="cell_two">N.Cellulare 2</label></th>
            <td>
                <input type="text" name="cell_two" id="cell_two" value="<?php echo esc_attr( get_the_author_meta( 'cell_two', $user->ID ) ); ?>" class="regular-text" /><br />
                <span class="description">Inserire il numero di cellulare n.2.</span>
            </td>
        </tr>
        <tr>
            <th><label for="cell">N.Cellulare</label></th>
            <td>
                <input type="text" name="cell" id="cell" value="<?php echo esc_attr( get_the_author_meta( 'cell', $user->ID ) ); ?>" class="regular-text" /><br />
                <span class="description">Inserire il numero di cellulare.</span>
            </td>
        </tr>
        <tr>
            <th><label for="conditions_of_payment">Conditions of Payment</label></th>
            <td>
                <select name="conditions_of_payment" id="conditions_of_payment">
                    <option value="option1" <?php selected( get_the_author_meta( 'conditions_of_payment', $user->ID ), 'option1' ); ?>>Option 1</option>
                    <option value="option2" <?php selected( get_the_author_meta( 'conditions_of_payment', $user->ID ), 'option2' ); ?>>Option 2</option>
                    <!-- Add more options as needed -->
                </select>
                <br />
                <span class="description">Select the conditions of payment for this agency.</span>
            </td>
        </tr>
    </table>
<?php }

// Save the extra fields
add_action( 'personal_options_update', 'my_save_extra_profile_fields' );
add_action( 'edit_user_profile_update', 'my_save_extra_profile_fields' );
function my_save_extra_profile_fields( $user_id ) {
    if ( ! current_user_can( 'edit_user', $user_id ) ) {
        return false;
    }
    update_user_meta( $user_id, 'cell_two', sanitize_text_field( $_POST['cell_two'] ) );
    update_user_meta( $user_id, 'richiesta', sanitize_text_field( $_POST['richiesta'] ) );
    update_user_meta( $user_id, 'cell', sanitize_text_field( $_POST['cell'] ) );
    update_user_meta( $user_id, 'conditions_of_payment', sanitize_text_field( $_POST['conditions_of_payment'] ) );
}

I suppose I have to create 2 fields with the same Id or meta_key, but how can I tell the system which value must prevail?

This is an example of a numeric custom field in my post editor

// ACTION TO ADD A META BOX NUMBER

add_action( 'add_meta_boxes_post', "number_add_meta_box" );

/*
 * Routine to add a meta box.  Called via a filter hook once WordPress is initialized
 */
function number_add_meta_box(){
    add_meta_box(
        "number_meta_box",  // An ID for the Meta Box.  Make it unique to your plugin
        __( "Distanza dal mare", 'textdomain' ),  // The title for your Meta Box
        "number_meta_box_render",  // A callback function to fill the Meta Box with the desired UI in the editor
        "post",  // The screen name - in this case the name of our custom post type
        "side"  // The context or placement for the meta box.  Choose "normal", "side" or "advanced"
    );
}

/*
 * Routine to display a custom meta box editor
 * Note: In this example our custom meta data is saved as a row in the postmeta database table.
 * $post PostObject An object representing a WordPress post that is currently being loaded in the post editor.
 */
function number_meta_box_render( $post ){

    // Get the number and display it in a numeric field
    $number = get_post_meta( $post->ID, "function_number", true );
    echo '<div><input type="number" name="function_number" value="'.$number.'" placeholder="Distanza dal mare" /></div>';
 
}

// Hook into the save routine for posts
add_action( 'save_post', 'number_meta_box_save');

/*
 * Routine to save the custom post meta data from the editor
 * Note: We retrieve the form data through the PHP Global $_POST
 * $post_id int The ID of the post being saved
 */
function number_meta_box_save( $post_id ){
     
    // Check to see if this is our custom post type (remove this check if applying the meta box globally)
    if($_POST['post_type'] == "post"){
        
        // Retrieve the values from the form
        $number = $_POST['function_number'];
        

        // Clean, sanitize and validate the input as appropriate

        // Save the updated data into the custom post meta database table
        update_post_meta( $post_id, "function_number", $number );
        

    }     
}