Why is it already busy with something when mounting an empty container in VeraCrypt?

Question

Encryption

I haven't seen this in truecrypt.
Created a regular container file in VeraCrypt. Its size was set to 100 MB.
I check in the explorer - everything is right, here it is my 100 MB file.
I mount it on the Z drive.
I look at the Z drive in the explorer. The size of the disk is 100 MB. But about 84 MB free, 16 MB used. Unclear.
I open - the disk is empty. Explorer / system / location glitch?
I copy files to this disk. More than 84 MB does not copy.
Why is it already busy with something when mounting an empty container in VeraCrypt? And what is he doing at 16%?
PS
16% is a lot.

Answer 1

NTFS file table.

Answer 2

maybe System Volume Information and the like?