I guess I just don't get it.
I still don't get how you are coming up with the numbers at the end of the command
You mention 20971520 is the end sector you need but then your command
Create a partition by running partedUtil set "/vmfs/devices/disks/naa.60050768018180732000000000000e9a" "1 2048 20964824 251 0"
does not have the number 20971520 listed anywhere in that command