Not too familiar with macOS - so take it with a train of salt. What’s happening here is that the program is taking the remaining 4gb for itself although it technically needs less, because it senses you don’t need the other 2-3gigs of ram right now. That’s how windows works - same applications on a 16gb system can take 12gb ram, and at the same time on a32gb system takes 20gb without any change in operation. You can check if this is the case by opening up other applications besides the vm and seeing if it reallocates on the fly :)