Which files are being backed up by Time Machine?

If you are curious about which files are being backed up by Time Machine, you can use a command line tool named timedog. Ensure your backup disk is mounted.

cd "/Volumes/Time Machine/Backups.backupdb/[Computer Name]"

Then run time dog for example with a directory depth of 8.

timedog -d 8 -l

This lists the files backed up with in most recent iteration.

You may skip big files that often change but you don't need to be saved e.g. games. Add these directories to excluded dirs in
System Preferences - Time Machine - Advanced.