This is very similar to this problem: https://xenforo.com/community/threads/gallery-statistics-all-zero.88247/
But something strange happened here. The cronjob "Update XenForo Media Gallery Statistics" has been running during the past days apparently just fine (I was monitoring their "Next Run" and it always kept changing which I guess means that the cronjob has been running), however the Gallery Statistics block was displaying everything with a value of 0.
Now I manually ran the "Update XenForo Media Gallery Statistics" cronjob and it said "Cron was run successfully". Now my "Gallery Statistics" blocks is displaying the (apparently) proper values.
This is strange because if the cronjob has been auomatically running I don't know why I was getting 0 values and now that I ran the cronjob manually it got fixed. It's rare.