I was wondering if you could include in Appointment+

Hi, I was wondering if you could include in Appointment+ the ability to book appointments in 15 minutes interval. My business needs require me to book appointments in 15, 30 or 45 minute time slot. For instance, if I need to schedule a client appointment at 3:45pm, the plugin does not allow me to do that. I would certainly appreciate your help with this. Thanks.