Why are file sizes on my phone and computer different?

[AC Question]

I downloaded a file on my phone (Xiaomi MI4) which was shown as 4.1GB on my phone storage, but when I plugged the phone into a computer via USB, the shown file size on the computer is much smaller than what is shown on the phone (only a few hundred megabytes), but somehow increases overtime, increasing to 3.85GB for the file in question. I am sure I fully downloaded the file. I proceeded to transfer the file into the computer but I have no idea whether it is working or not. Is this normal or have I done something horribly wrong?

 

[MoboPlay]

It's normal that it takes some time for the computer to read the full size of a large file. And it's normal that the size shown increases over time within a few seconds. The data shown on the phone is correct. Don't worry.