Yes, you can overbook sessions, if you want to.
A room is overbooked if the number of children you've booked in is 'more than the number of spaces available'. Your occupancy calendar will highlight overbooked days in red. This view will only be available to you - and not your customers.
What will my customers see if I am overbooked for a day?
Cheqdin typically displays available spaces to parents on your centre's CheqBook based on the 'net free capacity' on your occupancy calendar. For example, if your occupancy percentage is 100% (fully booked) or >100% (overbooked), your customers will be prevented from making a booking and will be shown a message saying 'there are no available sessions' for the day.
Now, If you change your mind later and you want to make more spaces available to your customers for online booking, all you need to do is cancel the unwanted sessions from your 'online bookings' dashboard. The cancelled sessions will be automatically made available as free spaces for your customers to book online.
You can also block or unblock dates in your calendar depending on the number of sessions you want to be displayed as available to your customers.