I've enabled "Delete cookies and site data when Firefox is closed" but while all cookies gets deleted, some random site data does not. Are my settings wrong, is this a bug, and what even is that data?
Additional Info: I use RFP, want to keep browsing history and site settings. Thank you very much.
Except the actual content is very likely boilerplate stuff.
My point still stands. The size of data says nothing about its contents. If OP is concerned about this from a security or privacy perspective, you shouldn't be writing them off because it's only 100 bytes.