Machine: FW13 AMD 7840U (BIOS 3.03) with Crucial DDR5-5600 48GBx2.
OS: Microsoft Windows 11 23H2.
I change iGPU Configuration which in BIOS setting between UMA_Auto and UMA_Game_Optimized. Then I run FINAL FANTASY XIV: Endwalker Official Benchmark and FurMark 1.37.2.0, but I can’t see a significant difference. I use GPU-Z and Windows task manager to view GPU memory size. I cannot see significant difference, too.
Is this because my main memory large than 48GB? Because I see total available graphic memory is 48GB in task manager and video graphic card properties. I guess UMA_Game_Optimized have better effect when main memory less than 32GB because more VRAM reserved.
All that setting does is increase the statically allocated gpu memory. For most applications this should not make much of a difference (they can request as much as half of the host memory if they want to). This basically mostly helps with applications that can’t or won’t request the additional memory they need right or “check” if there is enough memory before requesting it and then refuse to try.
I don’t think the available memory has an impact on the statically allocated memory but it does influence how much it can dynamically request.
The problem is gone after I update Windows 11 and install latest AMD official driver.
Now it will show 4GB dedicated GPU memory in Windows Task Manager and GPU-Z when UMA_Game_Optimized is enable. It’s show 448MB dedicated GPU memory in Windows Task Manager, 512MB in GPU-Z when I set to UMA_Auto.
Actually, 448MB dedicated GPU memory in Windows Task Manager, 512MB in GPU-Z when I set to UMA_GAME_OPTIMIZED again after I send previous post several days.
As a user which use PC from Intel 386SX, DOS 3.3 and all PC is assembly by myself,
I cannot think behavior cannot predict is normal. I contact support at 1/19/2024 and communicate by mails, but they just say it is normal. 
Are you on the latest BIOS update? Framework Laptop BIOS and Driver Releases (AMD Ryzen™ 7040 Series)
Also, bear with me as this may seem like an extremely obvious question, but when you swapped from Auto to Game Optimized, did you save the settings in the BIOS before exiting?
I’ve just left it set to Game Optimized after I first got the laptop, latest BIOS version, can’t say I’m really having any issues with it not showing the correct amount of VRAM in Task Manager.
When my FW13AMD (7840U) shipped at Nov.2023, it’s BIOS already v3.03 (current version).
And I executed BIOS v3.03 update program at Dec.2023 for solve Dell P3424WE USB-C Monitor KVM/PD charge and iGPU memory config issue.
I use MS-Windows Taskmanager, GPU-Z, HWInfo to check iGPU memory config.
I also use Pop!_OS checked by command "glxinfo | grep -E -i ‘device|memory’ "
In Dec 2023 several days, it has been show 4GB. I use FINAL FANTASY XIV: Endwalker Official Benchmark, it had 5~10% score better than 512MB.
I install 48GB*2 in my FW13AMD.
After customer service say it normal (not we will solve these issue in future),
because My FW13AMD is stable, so I give up to process and debug iGPU issue.
But I think I may not buy FW13 more expensive product line like i7-1360P/i7-1370P/7840U in future.
AMD iGPU (of 7640U/7840U) with more dedicated RAM config:
(1) Change BIOS config from UMA_AUTO to UMA_GAME_OPTIMIZED.
Please reference Framework knowledgebase.
(2) In MS-Windows, launch AMD GPU config GUI (AMD Software Adrenalin Edition).
Change setting at performance/Tuning/Memory Optimizer from Productivity to GAMING.
Change setting NEED REBOOT for work.
(3) User can confirm result by GPU-Z, HWInfo or Windows Task Manager under MS-Windows.
Use " glxinfo | grep -E -i ‘device|memory’ " command under Pop!_OS.
I think Ubuntu maybe work too.
(4) Dedicated RAM should 4GB now.