What is needed?

It should be clear in the document that access keys require write permissions for it to be used in the Branch permissions.

• When adding branch permissions at the project level, Bitbucket searches for access keys with the "Project write" permission.
• When adding branch permissions at the repository level, Bitbucket searches for access keys with either the "Project write" or the "Repository write" permissions.

What should it say?

Current: Adding a user, group, or access key as an exemption means that restriction will not apply to them. 

Ideal: Adding a user, group, or an access key with write permission as an exemption means that restriction will not apply to them. 

What is the document link? 

https://confluence.atlassian.com/bitbucketserver0721/using-branch-permissions-1115665647.html

https://confluence.atlassian.com/bitbucketserver/using-branch-permissions-776639807.html