What have you got in there that takes up 30MB?
How old is it?
Start some house keeping and delete some of the older stuff,say if it went into the chest some time ago and your computer is running ok (e.g. no system files have been sent to the chest). Then it would be reasonably safe to delete older entries from the chest.
The chest should be a temporary location where you investigate an infection and ensure that it is not a false positive, check the forums, google search, etc. and that no harm will come of your system if you delete it from the chest.