How to reproduce:
1. Install any style with multiple customized templates
2. In admin panel in styles section select "Customized Components", select your style.
3. Write something in filter to show only few templates ("author" on screenshot below)
4. Check box to select all items
5. Click "Revert Selected Items" button.
After doing all those steps you'll get overlay asking if you want to revert all templates. It will show total number of customized templates instead of only selected templates. That is not a typo - after clicking button to confirm action XF will revert all customized templates.