Windows user folder size less than actual size

I have a question about Windows user folder size.

I'm using Windows 10 latest version, let's denote my pc user name as abc. When I right click the folder c:\users\abc and select Properties, Windows tells me the size of this folder is 16.7 GB.

But when I open this folder c:\users\abc, select all sub-folders, like documents, downloads, ... again right click to see properties, Windows now tells me the size is 49.2 GB, which is the actual size.

I didn't create any symlinks nor hidden files here. So why there is so huge the difference? BTW, this only happens to my user folder c:\users\abc, other directories seem pretty fine with size display.

Edit 1: I'm not asking how to get or visualize the correct folder size. My question is why the two displayed sizes are so different? Also, in my case, it's the folder size 'much less' than the actual size, not 'more' than, nor 'slightly different from'.