Why Terra Master NAS takes extra disk space to store files?

[xmcheng]

My Terra Master is F2-210. I configured it as:
Raid Type Single disk
Volume name Volume #1
Volume Capacity 4.00TB
Selected Disk HDD1
File System Ext4
TOS 4.1.X

When I copy files/folders from a PC to the NAS through Windows File Explorer, the disk space taken on the NAS is much more than the space of the files. As in the attached picture "properties", the total space of the size for the files is 158 MB, but the space taken on the disk is 519 MB. Why NAS takes so much extra space. I have not tried to transfer files in other ways. Would be any differences?

DiskSpaceTakenByNAS.jpg

[Gremlin]

Could be differing block sizes.