How to store and get multiple values with single meta key

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Guys here the metabox query $text_pos = get_post_meta($post->ID, ‘dbt_postext’, true); which has and meta key of dbt_postext and i am facing the problem that there is one meta box which is basically for changing the text position of the slider according to the user inputted value..For eg if user passes 40 then the values go to here but i want that if user creates the 3 post for slider and pass 3 meta value at a time then how to add that 3 meta value to 3 post differently please help ??