If you have shared certain entries with multiple groups and the person was assigned to both groups, then they will continue to see all the passwords assigned to the second group. Below is an example.
Bob is assigned to the groups "Marketing" and "Sales" which each have the following entries shared with them:
Bob therefore has access to 5 accounts. You'll notice that the account "Brochures" has been shared with both groups. If you remove Bob from the group Marketing, but leave him in the group Sales, he will still have access to 2 accounts: Commissions and Brochures. So even though he was removed from the group Marketing, he still maintains access to any password entries (ex. Brochures) that are shared with any other groups he belongs to.