This is caused by the iCloud sync. It causes the creation of cache files. Unfortunately it is not possible to cleanup the cache folder automatically by Stage Traxx as these files are managed by iOS/macOS. Deleting these files just triggers the Cloud Sync system to recreate them.
Personally I have seen the cache to grow to 2-3 times the size of the actual data but in your case its 20 times the size. That's very extreme. Try disabling cloud sync and wait for a day or two and the cache files will be deleted.
