Hi user237,
Thank you for using Apple Support Communities.
I see that you are having an issue with the storage on your Mac running macOS Mojave. Used space is reported higher in error. I want to help. Have you tried rebuilding Spotlight and then checking again. Here’s How to rebuild the Spotlight index on your Mac – Apple Support
It can take some time to rebuild. After it is rebuilt, do you still see the same discrepancy? If so, boot into safe mode and check there. Here are a few quick notes about safe mode:
- Safe mode often looks and responds a bit different than what you're used to.
- Safe mode does not load everything that normally loads during a regular startup.
- Safe mode is a bit slower while loading and during normal operation as well.
- These differences can be cleared-up by a normal restart.
Here's how to boot into safe mode and Use safe mode to isolate issues with your Mac - Apple Support
Does the issue happen in safe mode? If not, restart again and try in typical mode. Just booting into safe mode in and of itself can resolve some issues.
I hope that helps. Reach back out with any questions.
Have a great day!