ResyOS overlap alerts warn you when a reservation you are booking or assigning overlaps with an existing reservation already assigned to that table.
You can temporarily disable the overlap warnings to allow you to more quickly rearrange or preassign reservations before a service.
To disable the ResyOS overlap alerts, tap the restaurant name in the top left corner and then tap 'Settings'.
From the reservations tab in your settings toggle off 'Show Reservation Overlap Alerts' to disable. The alerts can be reenabled on the iPad following the same steps.