Yes, you’ll notice that’s actually me reporting that as well. 480 GB * 0.01 = 4.8 GB, which makes sense here.
The problem is that it’s a percentage, so the larger the drive the more space is left unpartitioned. Unfortunately, we can’t simply use 100% using the tool as that corrupts the drive (no space to write the GPT table information), and the tool does not accept static spaces (like say 100mb) or tenths of a percent (like say 99.999% instead of 99%). This is currently the best automated solution, one that will hopefully be improved in the future.
As a workaround, you can always expand the partition yourself using gparted or a similar tool.
