With the current setup of Appointy, we don't have the blocking capability of 10 mins time interval. However here's a good workaround:
1. Login to your Admin area.
2. Go to SETTINGS>SERVICES>>Create "BLOCKED TIME" service with 10 minutes as service duration.
3. Disable this service, so that, it is not available for booking on the client calendar.
So, whenever you wish to block a 10 minutes slot, you can add a FAKE appointment from Appointy admin area, using the "BLOCKED TIME" service.
If you have any issues setting it up. Please let us know the details (along with your Appointy username) at firstname.lastname@example.org. And we'll be happy to do the needful.
Before you try out the workaround, here's a useful tip:
On the day view of Admin calendar, make sure to set the difference to 10 minutes (see the screenshot attached)