I want to accept two appointment applications for each time slot on Apointments+

I want to accept two appointments for each time slot since I have two service providers that have the same schedule and most of the time users do not notice the dropdown to select the other worker, I tried
function increase_capacity( $capacity, $service_id, $worker_id ) {
return 10;
add_filter( 'app_get_capacity', 'increase_capacity', 10, 3 );

filter you suggested on FAQ, however seems it doesn't work.
nikalabs/163Genesis! is the credentials for the dev website.