You can slide matches around in the surfaces scheduler. But you'll notice that if you are set to the hour, you won't be able to be precise with the times specially if you want the half hour or 15 minutes.

To be able to drop to 7:15 or 7:30 etc. in the surfaces scheduler:

Go to Surfaces scheduler (Menu > Manage > Schedule/Charts > Surfaces Scheduler)

Click on the word Hour,

Set it to the minutes you need, 10 minutes, 15 minutes, 30 minutes.

Choose the time slot you want.