URL Cache Dir1 File Almost 10GB

Good Afternoon All

We are currently using Forefront TMG 2010 W/ SP2, recently we have been running out of space on our Windows 2008 R2 server. After investigation i have found a file called DIR1 which is the folder URLCache which is 9.68GB ?

My question is does it need to be this big, can it be compressed/capped to a certain size?

Any help would be much appreciated.

Thanks,