To set the max number of people you are happy to be auto-confirmed. E.g. For dinner bookings, I am happy to auto-confirm any bookings under 6 people.
Venues > choose the venue
Booking Types > choose a booking type
Scroll down to Auto-confirm Rules
Tick the days you want your auto-confirm rules to apply to
Input the min & max number of guests and the time parameters (you can leave ANY TIME if you are happy for the availability rules to apply)
Make sure to SAVE the page
NB - make sure to also complete the AREAS FOR THIS BOOKING TYPE section, for the rules to take effect