i don't know the exact numbers, but from my experimenting, i think it is +1 to +6. scaling at E would mean +1 base damage for every attribute point and scaling at S would be +6 damage for every attribute point. so, if a weapon scales at A with intelligence, then the base damage of the weapon would increase by 5 points for every attribute point you have in intelligence.
let's say the sword of astoria, for example, scales at B/B/C/C, so it gains +4 damage for every attribute point in STR and DEX, and +3 for every attribute point in INT/FAITH (i'm at work right now and don't remember the scaling on it. may be CCDD or DDCC...all i know is it scales at D or better for all 4 attributes). this seems trivial, but it can add up pretty fast. my build is 40 STR, 45 DEX, 36 INT and 20 FAITH, so i am taking the 200 or so base damage of the sword, and the scaling adds 160 for my STR, 180 for my DEX, 108 for my INT and 60 for my faith, assuming the scaling is accurate to the game.
combine all those numbers and then remember that the CRS scales by base +100% of right hand base damage at level 1 and iirc base + 150% at plus 5. so my right hand damage is around 700, and the CRS does 2.5X that, meaning i can one shot kill pretty much any enemy in PvP and any enemy in the game with the exception of some bosses that take 3-4 hits to kill. the CRS really needs to get patched out. that and the drake sword really break and simplify the game too much.
this is a kind of simplified explanation, though, as if it were 100% accurate, my CRS would do like 2500 damage and it only does about 1600. it isn't a straight +1 to +6...there are decimals in there that i'm not sure about. it is pretty close, and how it works, though, even if not precisely accurate. i could give you something more concrete if i were at home, but this hypothetical sword still explains it.
the harmless zombies outside of new londo have zero resistances, so you can go there and fool around with settings and weapons and test base damage on them.
