8 Minute Intervals for Appointments +

I'm trying to set up an Golf Course tee time sheet at 8 minute intervals. I have it all set up but the best I can do is set it up for 10 minute intervals which will not work for the golf course. I'm using the demo at http://outerbanks.cc/demo2/make-an-appointment/

If I use this plugin on a non network site can I make an adjustment using PHPMyAdmin to make it 8 minutes?