Negative storage size reported under Usage Quotas

Summary

Under Usage Quotas > Storage, and at the project page a negative size is sometimes reported for the storage usage.

Example Project

https://gitlab.com/beyondtracks/bmng-mbtiles demonstrates the issue it reports a negative size.

What is the current bug behavior?

What is the expected correct behavior?

I'm not sure if this is an error or not, but I don't understand how storage size can be negative, so assume it's a bug.