well firstly let's assume there's no parity bit in the first byte of the calculations, the first byte represents integers and the second which i think we can deduce exists from calculations not all being truncated to integer values* means that we have:
00000000.00000000 = 0.0
11111111.00000000 = 255.0
the part after the decimal point doesn't matter anyway;
so yes it would make sense for the numbers to be 0/255 - 255/255 where 127/255 = 0.498 and 128/255 = 0.502
there can't really be anything but 0 = 0/255 because where you have subtraction such as 5/255 - 5/255 = 0/255 you would want that to be zero rather than 0.004 unless you're programming was so poor you really wanted to convert every value up by 1/255 and put non-zero values in every field a character has, for example having a 0.004 triple attack value, which might not result in anything because the game could take up to the first 2dp without everyone having a tiny chance to triple attack; but it wouldn't make sense because of the conversion necessary.
*might be wrong about this? perhaps it is integer values of x/255 only which are converted to double bytes for the decimal value.
i'd assume this is a function of the ps2 to calculate in single bytes or at least not normally convert to decimal, because generally there is no difficulty using a pc to do so, i don't know enough about game code to be certain on this. i only know how to do some mathematics in c/++ in a sort of specialised way.
conveniently 0.004 won't make a difference to almost any of the calculations done by people already on dmg-% and similar because the lowest fraction they use is about 25/255 = 0.098 (or 1%)
i would be interested if someone could demonstrate it is 1-256 and why.
FUN FACT:
if you really need to convert to binary hold up your hands palms to your face, now hold up your fingers, up means a value of 1, down is a 0, in this example we will ignore the thumbs to give us 8 units - 1 byte (no parity bit)
right index is 1, right middle is 2, right ring is 4, right pinky is 8
left pinky is 16, left ring is 32, left middle is 64, left index is 128
this gives us 0-255, all fingers up is 128+64+32+16+8+4+2+1=255
0001,0011 = 19
0100,1000 = 72
etc.
using thumbs allows you to count to 1023^^
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