There is not enought space in your disco, try to install again.
59,90GB are ncessary.
22,85GB are available
You need more 37,05GB to realize your instalation
I think he’s saying that the Mac installation is much lighter than the Windows one.
When you install Unreal on Windows you can deselect stuff you don’t need and save some space, but I don’t think it will ever be 12GB, probably something’s different/missing/more optimized on the Mac version.