Thought it is late, but when I search related topic, I see this is not answered,
The summary you provide means you already used 5 users, but actually only 3 is actives. Not means you can add 2 users. Normally, the number of the 2 summary should be the same after you active all users added.
If you want to see how many users you can add, you should see the number one line above in the summary:
"Document CALs not allocated on server" as below. For my case, I still can add 4 users. And normally.