You can set a number of policies on the area administration page. Login to MRBS as an admin, go to the Rooms page, select the area in question and then scroll down to the policies section.

You can set limits on the maximum duration of any single booking, the maximum number of bookings and the total dutation of bookings. You can't set limits on the number of meeting rooms used, but you can prevent someone booking more than one room at the same time by setting in config.inc.php:

$prevent_simultaneous_bookings = true;

Policies only apply to ordinary users, not to admins.