More storage than exists

Hello!

I've just started bootcamp assistant and it went through the "erasing Time Machine snapshots" and afterwards I noticed a lot of space was freed up on my drive. Too much space.

It turns out both Finder and About This Mac are showing more space available than there should be on the drive.

See, by all accounts, this is a 500 GB drive (I'm unsure if that's correct since it was my dad's originally) but Disk Utility shows 500 GB and Macintosh HD is also shown as 500 GB. Now on About This Mac, it does split Macintosh HD and Macintosh HD - Data however Macintosh HD - Data is shown to have 499.96 GB free and Macintosh HD is shown to have… 512.25 GB free out of 499.96 GB!

So the reason why I'm bringing this up is that I need to know how much space I actually have free in order to create the partition for BootCamp, because I don't want to assume that I actually have 500GB free and assign 200GB if I actually only have 500GB hard drive with 224GB of files.

Screenshot below is from the About This Mac information

Second screenshot is what Finder shows

Last screenshot is what DiskUtility shows

Thanks a lot for the help!