Your design may only contain a simple object like a small cylinder with a hex recess in it - you would estimate the rough file size to be 7MB, but it ends up 70MB. How do you fix it?
This is a strange file size bug that occurs rarely with RSDOCS. In these cases, you should save the design as a STEP or SKP file and re-import. It should get rid of the excess info that is being stuck to the file.