How to make a s2member column in user admin sortable?

I have a user profile field setup and populated with a function that counts the days past the EOT. I’d like to be able to sort the users by this column so I can see who is the furthest past the eot. I got the column to sort, but it is not sorting by the right values:

//Now we make the column sortable
add_filter( 'manage_users_sortable_columns', 'efti_status_sortable_columns' );
function efti_status_sortable_columns( $columns ) {
    $columns['s2member_custom_field_days_past_last_eot'] = 'Days Past Last EOT';

    return $columns;


Hi AJ.

Where, the WP Admin > Users list?

What file is that code from, or is it yours?