Hi,
Issues history is not a distinct count measure, so if an issue has several Teams, it is counted for each Team. The distinct count of the issues history needs a custom formula, as described in this community post: Distinct count for Issue History - #2 by roberts.cacus
Unfortunately, this formula has a high risk of performance problems, and there is no feasible workaround for that currently.
Kindly,
Janis, eazyBI