Right now, the top of a board limits avatars to 6 users as per: https://jira.atlassian.com/browse/JSWCLOUD-17938 

When users exceed 6, a "+" icon is present and clicking this will show more users ("Online" and "Offline" users are listed in a larger list). However, this list is not definitive/consisting of all expected users. For example, a user may show up in "Online" when they are online (and the user has a Project Role/access to project). However, when that same user is offline, the user is not listed in "Offline" list.

When clicking "+", the list of users should be more consistent and potentially show a higher quantity of users. If some users are truncated and not shown, the UI could make this fact more clear.