Wow! In all my years doing this I've never see a support bundle that size! 
Typically they are a few hundred KB to a few MB and occasionally I've see some ~ 20 MB but never 300MB! To me a support bundle of that size indicates two possibilities, either something went wrong with the "VMware Fusion Problem Reporter.tool" script that creates the .tgz support bundle and I doubt that's the case and the other is you've had many issue/problems with either VMware Fusion and or OS X and the bundle contains lots of Core Dumps as that's what typically causes the .tgz file to be larger then normal.
Anyway, if you double-click the .tgz file on the Desktop and let it extract and then search the vm-mm-dd-yy.nnnn folder for any vmmcores-*.gz files and delete them. Then right-click the vm-mm-dd-yy.nnnn folder and select Compress "vm-mm-dd-yy.nnnn" and this will create a vm-mm-dd-yy.nnnn.zip file on the Desktop. What size is it now and if small enough then attach the vm-mm-dd-yy.nnnn.zip file to a reply.