Incorrect counter when choosing count_unique(users)

Hi there!
I’m new to sentry and I’m cleaning-up issues list by ignoring them with threshold
To make a correct threshold i use Discover graph to calculate peak of issues per hour for each issue
When i select count_unique(users) I expect to see only unique users in counter at bottom-left corner of chart, but it doesnt change.

To check that its an issue I exported csv and counted unique IDs of selected period to make sure there are less uniques than counted:

Actually there are only 22 unique and 61 total users.

Is it correct place to report bugs?
Is there any easier way to get required for ignoring stats other than looking for graph?