Discrepancy in Slack Community Member Count: Tightknit vs. Actual Numbers

Why would the number of members in our Slack community vary between what is shown in Tightknit and the actual number? Here's what I'm seeing:

If I remove deactivated accounts I get a slightly closer number in Slack of 437. Also looks like Tightknit might be including members across all account types including Invited which kind of skews the number actually in the community.