Modify WP Bookly Plugin

I need someone to write a Wordpress function for this plugin. I am using the Wordpress Bookly Plugin with Locations Addon from CodeCanyon. Currently the plugin works fine in most ways but it seems that Capacities Set on a Service are over ridden by Staff Capacities. If i set a capacity of 2 on a Service but enable 5 Staff members with a capacity of 1 each then this over rides the Service Capacity, which makes no sense at all. I need someone to modify this plugin so that regardless of how many staff are assigned, once the Service Capacity of 2 (or whatever number) is reached that no one can be booked for that Service at the given time slot. This requires someone who really knows the Bookly Plugin. This must be achieved by either building and add on, plugin or simply a custom function to the theme functions.php. No core Modification will be permitted. If it comes to a case of manually controlling capacities on a per service basis then an explanation of how to amend this in the future will be required. Do not quote unless you have read the description and can actually fix this at your quoted price.