Probabilities for chaos scrolls

I ran a debugger on the server stuff. Here's what I found. It's not bulletproof (pretty easy to find weaknesses in this algorithm I've posted), so I'll need more time with the function. Think of the following as a very good idea for how it should work.

Code:

def CalcRandStat(VariationType, StatOnWeapon):
  if VariationType == 0: # Gach item
    PossibleIterations = (StatOnWeapon / 5) + 1
    if PossibleIterations > 7:
      PossibleIterations = 7
  if VariationType == 1: # Regular weapon
    PossibleIterations = (StatOnWeapon / 5) + 1
    if PossibleIterations > 5:
      PossibleIterations = 5
  randStat = 0
  for Iter in range(PossibleIterations):
    randStat += getVariation()
  StatOnWeapon += randStat
  return StatOnWeapon

def getVariation():
  myVar = CRand32.Random()
  #complete guesses on these probabilities. But this is how the function works
  if myVar < 0.30:
    return -1
  if myVar < 0.70:
    return 0
  else:
    return 1