How to use it:
if chance = 1, 5
{
health + 1
That will heal you 1 point with the probability of 1 from every 5, that means 20% if you are not familiarized with fractions. Fractions are better than percentages because I don't think that PB will allow decimals, fractions can be used without decimals and will be equal to a decimal percentage, for example:
if chance = 1, 3
Will be a 33.3333333% of probability