SDL Modification

I understand the policy of the copy, paste and version number incrementation
I understand the Variable Default argument
I also understand the Variable Booleen function (0 = off & 1 = on)
But I am totally confused with the portion of the Var Byte Function - Just what values are usable???
Specially within the Neighborhood IE
# Performance variables
VAR BYTE nb01CallSoundChance[1] DEFAULT=0 DEFAULTOPTION=VAULT
# State variables
VAR BYTE nb01Ayhoheek5Man1State[1] DEFAULT=1 DEFAULTOPTION=VAULT
VAR BYTE nb01CommunityAreaState[1] DEFAULT=0 DEFAULTOPTION=VAULT
VAR BYTE nb01CityLightsArchState[1] DEFAULT=0 DEFAULTOPTION=VAULT
VAR BYTE nb01LakeLightState[1] DEFAULT=4 DEFAULTOPTION=VAULT
VAR BYTE nb01PrivateRoomsState[1] DEFAULT=0 DEFAULTOPTION=VAULT
VAR BYTE nb01PuzzleWallState[1] DEFAULT=0 DEFAULTOPTION=VAULT
VAR BYTE nb01StainedWindowOption[1] DEFAULT=0 DEFAULTOPTION=VAULT
# Randomized object appear/disappear
VAR BYTE nb01YeeshaPage07Chance[1] DEFAULT=0 DEFAULTOPTION=VAULT
VAR BYTE nb01DarkShapeSwimsChance[1] DEFAULT=0 DEFAULTOPTION=VAULT
VAR BYTE nb01BahroBoatsChance[1] DEFAULT=0 DEFAULTOPTION=VAULT
I understand the Variable Default argument
I also understand the Variable Booleen function (0 = off & 1 = on)
But I am totally confused with the portion of the Var Byte Function - Just what values are usable???
Specially within the Neighborhood IE
# Performance variables
VAR BYTE nb01CallSoundChance[1] DEFAULT=0 DEFAULTOPTION=VAULT
# State variables
VAR BYTE nb01Ayhoheek5Man1State[1] DEFAULT=1 DEFAULTOPTION=VAULT
VAR BYTE nb01CommunityAreaState[1] DEFAULT=0 DEFAULTOPTION=VAULT
VAR BYTE nb01CityLightsArchState[1] DEFAULT=0 DEFAULTOPTION=VAULT
VAR BYTE nb01LakeLightState[1] DEFAULT=4 DEFAULTOPTION=VAULT
VAR BYTE nb01PrivateRoomsState[1] DEFAULT=0 DEFAULTOPTION=VAULT
VAR BYTE nb01PuzzleWallState[1] DEFAULT=0 DEFAULTOPTION=VAULT
VAR BYTE nb01StainedWindowOption[1] DEFAULT=0 DEFAULTOPTION=VAULT
# Randomized object appear/disappear
VAR BYTE nb01YeeshaPage07Chance[1] DEFAULT=0 DEFAULTOPTION=VAULT
VAR BYTE nb01DarkShapeSwimsChance[1] DEFAULT=0 DEFAULTOPTION=VAULT
VAR BYTE nb01BahroBoatsChance[1] DEFAULT=0 DEFAULTOPTION=VAULT