I believe this has been reported many times but don't know if its actively being worked on or what so here goes!

If I set a Maximum Number of Values for CCK FUpload to 4 in Global Settings then the you are presented with 4 download slots on the page but if you upload using FUpload then you can upload 4 files each session thus getting around my limit of 4.

I think this is because the maximum number value is being used to determine swfupload's queue limit when really this needs to be worked out by taking away the current number of free slots from the maximum number to provide swfupload with number allowed to queue.