You can! In the Scheduling Limits page you can set how often you'd like to offer appointments on your calendars––such as every 30 minutes, 60 minutes, etc. If you'd like a calendar to offer appointments at a different interval than the setting in the Scheduling Limits, there's also an option for that.
Let’s say, for example, your Scheduling Limits offer appointments every 60 minutes, but you’d like to offer appointments at specific start times instead. In this scenario, instead of listing your availability as a set time like "9:00am-5:00pm", you'll list the exact times you'd like to offer appointments. So you'd list availability like "9:00am, 9:30am, 10:00am, 10:30am, 11:00am...". This way your other calendars will offer appointments on the hour, but one calendar will offer appointments on the half hour.