Virtualbox requests 261MB of VRAM or more but limited to 256MB

[ts]

$ lsb_release -rd
Description: Ubuntu 22.04.1 LTS
Release: 22.04

$ apt-cache policy virtualbox
virtualbox:
  Installed: 6.1.38-dfsg-3~ubuntu1.22.04.1
  Candidate: 6.1.38-dfsg-3~ubuntu1.22.04.1
  Version table:
 *** 6.1.38-dfsg-3~ubuntu1.22.04.1 500
        500 http://de.archive.ubuntu.com/ubuntu jammy-updates/multiverse amd64 Packages
        100 /var/lib/dpkg/status
     6.1.32-dfsg-1build1 500
        500 http://de.archive.ubuntu.com/ubuntu jammy/multiverse amd64 Packages

I'm creating a new VM (Windows 10 guest), I have one external 5K screen, I need a VM with two screens, I expect to perform settings so that I can use it (it worked in the past, although I'm not sure about my old settings as I removed the old VM before creating this one).

The interface tells me that at least 261MB of VRAM are required for the setup, the interface is limited to 128MB,
$ VBoxManage modifyvm "Name of VM" --vram 261

yields
VBoxManage: error: Invalid VRAM size: 261 MB (must be in range [0, 256] MB)
VBoxManage: error: Details: code NS_ERROR_INVALID_ARG (0x80070057), component GraphicsAdapterWrap, interface IGraphicsAdapter, callee nsISupports
VBoxManage: error: Context: "COMSETTER(VRAMSize)(ValueUnion.u32)" at line 671 of file VBoxManageModifyVM.cpp

Starting the machine at 256MB vram kills the second screen (even if I'd configure it to low resolution) when using the first screen on full screen full resolution (this is new, that was my common setup in my old VM).

I'm not bothered if I can actually have more than 256MB of vram or not (see all of the old threads), but I'd like to be able to use my machine on my setup (again)...

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: virtualbox 6.1.38-dfsg-3~ubuntu1.22.04.1
ProcVersionSignature: Ubuntu 5.15.0-48.54-generic 5.15.53
Uname: Linux 5.15.0-48-generic x86_64
ApportVersion: 2.20.11-0ubuntu82.1
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: MATE
Date: Fri Sep 30 12:03:21 2022
InstallationDate: Installed on 2022-03-07 (206 days ago)
InstallationMedia: Ubuntu 22.04 LTS "Jammy Jellyfish" - Alpha amd64 (20220228)
SourcePackage: virtualbox
UpgradeStatus: No upgrade log present (probably fresh install)