No option for 2.5Mb of video RAM. My Vaio (PCG-SR1K) has that amount. I used 2Mb as the next-best.
Sorry, but 2.5 MB is not a standard size. Anyway, the only significance of this is the screensizes/bit depths you are shown next - if you specify too much, no problem: You just need to make sure the mode doesn't use too much memory.
2.5 Megs of Video RAM are quite common on Laptops. I agree that selecting 2Mb won't break anything, but Linux novices might get into trouble at this point.
They probably wouldn't know they have 2.5 MB either ;)
Laptops do come with docs, you know. Opening up the glossy sheet to see what wonderful hardware I have, I see it quite clearly. Oh. 3Mb :) (But regardless, I am told that lots of neomagic cards come with 2.5!)