The guidance for groups in pubs reflects the current Government guidance for groups meeting generally. Currently this states:
Going to a pub or restaurant with members of another household
From 4 July, when eating or drinking out with people you do not live with, you should only meet one other household if you are seated indoors. People from more than two households at once cannot meet indoors. If you are eating or drinking outdoors, you can do so with one other household or in a group of up to 6 people from different households.
In all cases, people from different households should ensure they socially distance as much as possible. Premises should also take reasonable steps to help you do so in line with COVID-19 secure principles. It remains the case that you should only have close social contact with people you do not live with if you are in a support bubble with them.
This means that:
Two Households at the pub = allowed indoors or outdoors. Each household should remain socially-distanced from the other, but people within the same household do not. Anyone that has formed a “social bubble” with a household also does not need to remain socially-distant from that household, but they should remain so from the other household.
Up to 6 people from different households at the pub = only allowed outdoors. People should remain socially distant from each other.