numbers aren't pointless...it is how you look at it of course.
The max number thus far is 5.9, which would suggest if you have 5.9 then you can operate Vista 100% as it was designed. If you can, then perhaps it would also mean you could run all current games and all DX10 games as they come out....regardless of how demanding.
Now, they may refine it later on if DX11 comes out...but so far it is 5.9. This is not a scale from 1-10...but 1.0 to 5.9? Decimal increments count
Your rating is slight past mid range, which seems logical for the score. Mine is 5.3 with an E6600 and 2 gb ram, 512mb 1800.
Get an Intel FX or Q cpu...and maybe a NAND drive and your are good to go at 5.9 and all 10x games