Why is my RAM lower than what I paid for?
Your memory or RAM is not lower, it is only being allocated as needed by you. If you paid for a Windows VM with 4GB of RAM then you can use up to 4GB. So if your Windows VM is showing less than what your VM stats are for then that means you're using less RAM and more will be automatically allocated when needed up the maxmimum amount your VM is capable of.
You can see the maxmimum RAM capactiy of your VM in the Task Manager:
