hard drive – Free space shown on Windows 10 (BOOTCAMP partition) does not correspond to the free space shown on Disk Utility

I’m not quite sure how this works, but yesterday I used Boot Camp Assistant to get Windows on my Mac. Somehow the space available on the C drive is 10 GB whilst in the Disk Utility it shows 18 GB of free space on it.

I checked with the space analyser in the wizard tool partition to see where all the space went to (I have partitioned 30 GB for the BOOTCAMP partition and haven’t done anything on Windows, yet I only have 10 GB left already), it does show that there is only 10 GB of free space, but I’m confused as to why Disk Utility is showing different data.

I’m a little anxious about this because my Mac has low storage space to begin with so I’m worried that I installed Windows and can’t use it.

Also, if anyone knows about methods to free up some space would be great help.