You may want to add a check-in option for an open gym type of class where it could span multiple hours of the day.
Go to Apps -> Check-in App -> Configure.
Scroll to where you see 'Allow Open Gym Check-in'
Toggle that to 'YES'
Scroll to bottom of page to save
This will now show on your Check-in App
Now you should see this option on the iPad check-in app. Should be the first option.

Notes:
This won't be reflected on your class schedule, this is just a way to allow members to check-in to an open gym type class on the check-in app.