There are TWO types of video memory - Dedicated (DVM) and System (SVM). DVM is set in the BIOS. If there is no such setting in your bios, then there is nothing you can do. However, SVM may be able to be changed. Review this thread, post #2:
This message was posted on behalf of Intel Corporation
Al Hill, thanks for your valuable help
In regard to your concern, you will be able to change the capacity of your video memory according to the BIOS limitations of your system. If you the manufacturer of your equipment provide you with this option to change the configuration through the BIOS, there will be no problem.
The information provided by Al Hill will be very helpful, also after an extensive research, I was able to find some information that will assist you with your concern:
Frequently Asked Questions for Intel® Graphics Memory on Windows® 10
I am looking forward to hearing from you.