? Where do I specify frequency FCP backup?

I am trying to clean up my HD and noticed all the FCP backup files. I do not see where I specify the frequency of these backups. I do see where to specify the location of the backup.

The attached image shows a project with backups taken. The Sig Star project was worked on for months (hobby) yet I only see a hand full of backups all on one day and in different increments of time. How does FCP determine this?

All of my files are stored on two external HD's. I am trying to clean up the main HD to free up space. All the project files are leave in place.

Any help would be appreciated.

Rich

Roughly every 15 minutes when something in that Library has changed.