The group buffer is used if you want to auto-confirm multiple groups into one area but don't want to overfill it. For example, it can be used if you have any 'communal tables' with, say, a capacity of 10 and where you are happy to put a group of 6 and 3 into that same area but at the same time don't want to put two groups of 5.
A "multi-group" buffer gives the two groups some breathing space. So, in the area of 10, if two groups were auto-confirmed into it, you could ensure that only 9 people will be auto-confirmed, e.g. a group of 6 and 3. To do this, the multi-group buffer for this table would be 1.
> Tables/Areas tab
Alongside the relevant area, fill out the "Multi-group buffer" box.