Is "Reviewed" what happens when you e.g. vote or something then click I'm Done?
"Reviewed" is always the result of doing something and then clicking "I'm Done". That can be flagging the post, up- or down-voting, commenting or editing.
It's the same for audits, although you do not explicitly need to click the button, since the audit gets revealed before.
In your particular audit case, the first user has chosen "No Action Needed" and the second user most likely up-voted the post, which is counted as a "Reviewed" action. It couldn't have been down-voting or flagging, since the user would have failed the audit then.
I reproduced that with this audit by up-voting the post.
Yes, "Reviewed" is the outcome that is shown when you click "I'm Done", as opposed to "No Action Needed". From the documentation in the review page for First Posts:
No Action Needed when this post needs no action from you.
I'm Done is only available if you've done one of the following:
- Vote up or down to rate the question's quality and usefulness
- Edit to improve the question's appearance or clarity
- Comment to leave constructive feedback for the author, or vote up existing comments
- Flag to notify the moderators of serious problems
- Close questions that cannot or should not be answered here
Be sure to leave a comment if you can help the user out, upvote the question if you can't find any problems with it, or click Skip if you are not sure and want to go to the next item.
(this should also show voting to delete if you have that privilege on a site)
"Reviewed" is only present in the First Posts and Late Answers queues, because these both allow you to do pretty much anything during a review, unlike other queues, where you must explicitly choose an action, e.g. "Close" or "Recommend Deletion".
Presumably, "Reviewed" is used instead of actually listing the action to avoid disclosing which way you voted, and if you flagged or not (and to avoid the complexity of listing every action you did). In the other queues, the actions you take would have been public anyway, so your choices can safely be displayed.
The discrepancy between displaying "Reviewed" and "I'm Done" is probably just stylistic—saying a user voted "I'm Done" would look a little strange and not be very clear to others!