You applied a quota via FSRM and saved some files... After a while you can´t save more file cause Quota Management is thinking you have reached your quota limit...
Quota Management showing "Used: 300 MB (100%)".
If you check the size of the affected folder, you see that only 576 KB are in use.
So something is wrong with the quota scan. To solve this you have to trigger a quota scan. To do this type in the following command via cmd on your File Server:
dirquota quota scan /path:Z:\YOURPATH
Now your quota is working properly!
Update:There is a hotfix from MS available:
THX to Xyybyral for saring this info!