Hi,
Currently it is programmatically limitet to the 3 folds of the current limit, as you noticed. With the custom post types search this is increased to 10 fold. It is due to performance and a few other reasons.
The only way to increase it currently is by making direct changes to the core plugin code. There is a query argument added that will work in the future releases via a custom code, but not with the current one unfortunately. However I can suggest a modification and a custom code, that will increase this limit (to infinite), patches the current version, and will work in the future one as well:
1. Make sure to have a full site back-up just in case
2. Open up the wp-content/plugins/ajax-search-pro/includes/classes/search/class-asp-search-users.php file on your server
3. Replace it’s contents with this
4. Save the file
Now, a few lines of custom code is also needed. Try adding this custom code to the functions.php in your theme/child theme directory. Before editing, please make sure to have a full site back-up just in case!
add_filter( 'asp_query_args', 'asp_change_remaining_limit_mod', 10, 2 );
function asp_change_remaining_limit_mod( $args, $id ) {
$args['_remaining_limit_mod'] = 9999999;
return $args;
}With these changes, the limit should be lifted. Just make sure to keep the custom code above in your functions.php file, and it will be fine in the upcoming updates as well.