Custom Scheduling / Block Scheduling / Custom Times / Documentation

Can you please provide some documentation on how to make custom scheduling times? For example I want to start at:

7:30am
10:30am
1:00pm
4:00pm

Each appointment is 2:30hrs / 150min.

We have a semi-detailed solution here

Could you just provide some more documentation so I can make changes as necessary?

Here is the specific code that I would assume is needed - some documentation on how it works / how one could change it to suit their own needs.

function add_some_minutes( $ccs ) {
	if ( date( 'G', $ccs ) >= 14 )
		return ( $ccs + 1200 );
	if ( date( 'G', $ccs ) >= 12 )
		return ( $ccs + 1800 );
	else
		return $ccs;
}
add_filter( 'app_ccs', 'add_some_minutes' );