You can specify the time of day, but the add-on won’t do anything faster than once a day.
If you want a more custom schedule, you can set time_between_snapshots=0, which will prevent the add-on from creating snapshots on a schedule, and then create an automation that calls the hassio.full_snapshot service to create snapshots using whatever rules and intervals you configure it with. The add-on will still upload snapshots you create like this to Google Drive, cleanup old ones, etc.
Out of curiosity, what are you doing that makes hourly snapshots desirable? Even daily seems like overkill to me.