Why is my phone memory full (4.21 Gb) when its folders only take 1.2 Gb?

[AC Question]

My phone (samsung J3) is telling me it has almost no space left. When I connect it on my PC, it says the internal memory has 4.2 Gb used. But When I select all the folders inc. hidden ones and that I check properties, it says it's using 1.2 Gb... and there's no file at the root of the internal memory...

Any idea?

Thanks!

 

[AlphaTango414]

Settings>System>Storage this will show you the better picture. Majority of your memory will be taken up by system files aka the Android OS. My GS7 Active OS takes little over 9GB for example.