Kaufmann Risk of Ruin formula

scalpmaster

Has anyone used this formula before?
www.trade2win.com/traderpedia/Risk_of_ruin

risk_of_ruin = ((1 - Edge)/(1 + Edge)) ^ Capital_Units
Edge is the probability of a win.

How is capital_units defined? Is it certain % of current balance or initial capital?

If p=0.5, e.g,fair coin toss,
how is the formula derived such that ROR always= 0.5/(1+0.5) or 1/3 of capital units?
Is there a rationale behind this?

Looking for a formula to work backwards for optimal bet size each round of bet , taking into account p,q,C,N where N = max consecutive/string of losses.
N is an important variable because total ruin can still occur even when p>0.5.

Related free ROR calculator
http://www.automated-trading-system...n-and-drawdown-