The passes won't double if you run it the way you've mentioned above. Also, the developers created a page with details regarding the Wipe Space function found in the CCleaner application.
Here is the page: https://www.piriform.com/docs/ccleaner/using-ccleaner/wiping-free-disk-space
According to the page, there are the limitations regarding the Wipe Free Space:
- The file has been overwritten by another file (so no need to overwrite this again)
- The file had been overwritten by another file before you ran CCleaner, but the second file has now been deleted as well.
- The file was created almost exactly when you ran CCleaner.