4GB installed. I looked at /var/vm/sleepimage before and after a reboot and it was 4GB in both cases (at least according to ls). The variation in free memory is greater than the memory I have installed anyway. I didn't however realize that /var/vm existed and contains pointers to the other swapfiles that I can monitor to see how they change. Thanks for the tip!
There is a way to disable sleepimage, but I'd rather not say it, since you should really clean up your disk.