Hello,
I have also experienced this sometimes. I don’t know exactly what causes this, but rescheduling actions or rare bugs are the main reasons.
You said it was a one-time thing, and it’s probably not a recurring issue. This will not cause many problems with your studies.
If this really bothers you, the only way I know to revert this is to restore from a backup. You have to pick a time/day before this happened. Your collection will be restored to that time, so anything between that backup and now will be nonexistent. So you will have to do your reviews again.
Restore from backup tutorial: How to Restore from Backup
But as I see in your Anki, the review count differs from the heatmap add-on. So maybe it’s just an add-on bug.
Let me know if you need help with anything else. 