To copy a group booking allows you to multiply this booking to a later arrival date, but to keep the same rooms/beds.

To create a copy of a group booking, click the "Copy Group" button on the booking page of the group booking. 

On the next screen, select a later arrival date, the rates, and if you want to assign this copy to a new booking number or to the existing one you are copying it from. 

Confirm with "Copy".