Booking into a session after start time

Hi there, I have created some super sessions for our gym users to widen their time choice but I want them to be able to still book after the session has started if there are spaces available. For example a session may start 8.00-12.00 and allow 60 spaces. At the minute our customers cant book once the session has started even though there are plenty of spaces. Is it possible to have an option so we can allow booking throughout the session? For classes we can’t allow this but for gym sessions it would be good.