I believe this page needs to make it more clear that the permissions set on this page are default permissions that will be applied to all repositories.
The current text for each group says 'Admins have <read/write/no/etc> access to this account's repositories'
I propose it should say 'Admins have default <read/write/no/etc> access to this account's repositories'.
Here is what got me to this scenario.
All I wanted to do was create a group, add users to the group, and give the users of the group write permissions to one repository.
Instead of knowing to set the access to 'no' for the group and adding the group to the repository, I had to spend over an hour of searching and reading documentation to understand this (seeing the word default in the documentation on your website).
The current way it's written is confusing and would be easily solved by having the word 'default'. It makes me think that if you select 'No' for a group, the user/group will have no access to any repository no matter what. It could also mean that those are the highest possible permissions for people in the group and it can only get more restrictive when setting stuff under the repository's permissions.
I don't see how adding this word in a couple spots on the page will harm productivity, but I do see how omitting it hinders productivity. Default needs to appear somewhere on this page in order to clear up this confusion.