I'm confused why you would hide a user count from me.
If I go to the Subscription page in the Billing section of my Opsgenie instance, it tells me I have 160 seats/licenses. And... hooray, it will email me when I hit a threshold I can modify.

If I go to the Billing section on my Atlassian account, it leaves me suspiciously uninformed, as you can see by the cross-section in the following screenshot. And if I click on "Manage"? It brings me back to the page of the first screenshot.

FURTHER... if I go back to my user directory, and filter by both "active" and "Opsgenie", it still doesn't give me a "count" of how many active Opsgenie user licenses have been found! The count includes ALL my active users, as seen here:

So, again. Why is Atlassian being deceptive here?
It is only when I go to the "users" section in Opsgenie that I can get any functional result.

There is NO REASON that, on either of my billing pages, Atlassian could not provide how many active users I have... just like with every single other product or add-on they have. Again... as seen above in my screenshot.