haha! I bet nobody ever knew this! And this is not an April Fool's thing. Seriously. It isn't.
Screenshot Captor has the Y2K problem! It cannot number screenshots past 999!
Really! So, I set my SC to name screenshots like this: Screenshot_1.png Screenshot_2.png
but once it gets to Screenshot_999.png, it can't create Screenshot_1000.png and just keeps overwriting Screenshot_999.png.
Here is the setting at Settings > File Naming> New Screenshot File Template > Default New File Name
And, I have checked the box in the same settings section for "Auto sequence new file names to avoid overwriting old files"
Auto-incrementing Number is set to "1"
For myself, I've modified the naming scheme to: %quickfield% Screenshot2022%_num% to get it to start the numbering over at 1.