I use a surface pro and moved some work files from my desktop which I know to be over 10gb to my surface which now insists the folder is 905 mb and 603 files which I know is wrong. The folder has several sub folders one of which is over 10gb by itself. if you check the folders individually the size is credible but selecting all the folders and the reported file size is less than the largest folder alone by a big margin.
my pc just updated to build 1803 and in see others have the same issues - come on Microsoft lets get the basics right!