Change below minimum base time slot

Hello @justcam

Hope you are doing well!

Please add the following line at the bottom of functions.php file of your active theme

add_filter( 'app-time-min_time', function(){return 5;}, 20 );

This will add additional base time to service and you can create services with 10 and 15 minutes duration.

I suggest adding these lines into the Child theme, because after an update changes in the functions.php file will be lost. If you do not have a child theme, please see here how to create one:
https://codex.wordpress.org/Child_Themes

Let us know how it went!

Cheers,
Nastia