More than 10 Pro/Con/Options

I need more than 10 Pros/Cons for one of my clients.

It seems to me that a select box for this is rather limiting and allowing the user to put in whatever number they like would be the better way to go.

I thought maybe I could filter it, but I’m not having any luck.

Here is what I tried

add_filter( 'wppr_settings_fields', 'csm_wppr_add_pro_con' );

function csm_wppr_add_pro_con( $arr ) {

    $arr['cwppos_option_nr']['options'] = array(
            '3'  => '3',
            '4'  => '4',
            '5'  => '5',
            '6'  => '6',
            '7'  => '7',
            '8'  => '8',
            '9'  => '9',
            '10' => '10',
            '11' => '11',
    );

    return $arr;
}

Any help in achieving this would be appreciated.