Why does zabbix show different data?

Question

Monitoring

There are several windows server 2012 r2 as virtual machines on proxmox. They have zabbix agents installed inside them. I created an Item to monitor the total-free-used space on drives C, D ....
In the process, I noticed that the data that I see in the zabbix north and in "This computer" of the virtual machine itself is a little, but still different, for example,
Windows drive C: total 199Gb, free 101Gb
Zabbix Server C : total 214, free 109Gb
The images of these disks in proxmox themselves are in the qcow2 format
Why is this happening?

Answer 1

Most likely, the difference is that one counts in GB and the other in Gb, but this is just a guess.