I cannot create a partition on my C: drive

Support.com

1-833-202-2695

I’m trying to create a partition on my C: drive to be able to dual boot Ubuntu rather than having to live boot, but while disk management says I have 19.26 GB left(as does settings-system-storage), when I try to shrink the drive, it says I have 0B of available shrink space

partition tech support picture.JPG

I also tried it from the terminal with diskpart but it says I have 0B free on my C: drive as well

330318
Support.com Number