How do I add "padding" to time slots?

Hi, Des_Walsh had a similar question, but I need code to reflect my situation.

I want people to be able to book in 30 minute intervals, eg. 9.30, 10, 10.30,11 etc, for sessions that last 90 min. PLUS have 30 minutes padding to prepare for next session. How would I modify the code below that Hakan recommended?

See: function modify_duration_text( $text, $duration ) {

return ’30 minutes’;

}

add_filter(‘app_confirmation_lasts’, ‘modify_duration_text’, 10, 2);

Because I dont want the customer to see 120 min in their receipt, I cant just set the duration to 120.

AND I want people to still have time slots available every 30 minutes. If I set it to 90 minutes, eg 9am, 10.30am, 12pm I miss out if someone wants to start at 9.30 as that is not possible.

Hope you can help, thanks Hart