Open the app - https://admin.timerise.io.
Go to the Services section.
Choose a Service.
Select the Schedule tab.
Click the Add Availability button or click the Edit button next to one of the availabilities.
In the Bookings per slot input, type the preferred number of people who will be allowed to book the same time slot.
Click Save.
Additionally, to let your customers see how many free slots are left for a given date on the booking pages, go to the Display tab.
Select the Show available bookings per slot option.
Click Save.
Now, your customers will be able to book the same time slot.