You understand correctly. Adding a graphics card will release that RAM currently dedicated to video use. When your system is set in BIOS to use the graphics chip included in your CPU, it also allocates some main RAM for that purpose. But when you install a graphics card and change the BIOS setting to use that instead, the BIOS will not allocate any main RAM for video. It assumes (correctly) that the video card has all of its own RAM that it needs. Actually, when you install that video card, the utility that you run to install the drivers for that card will make that setting change in BIOS for you - you do not do that yourself. If you want to see all that, boot your system before installing the new card, and check for Free RAM space. After the installation, check that again to seee the change.