You can get rid of this message by disabling “Pool Auto Grow in Editor”
After turning it off, message no longer appears, but since VT pool settings seem like deeply technical topic, I don’t have a good understanding how turning off this feature will affect performance or visual quality of the level.
If I have to make an educated guess, I’d expect it to cause issues with some materials not always displaying sufficient/full resolution of virtual texture if the memory pool is filled, even if GPU has more free VRAM available to fill.
But since it’s Editor-only setting, it’s probably relatively safe. The tooltip is implying the auto-growth is disabled in cooked builds by default anyway.