# How is ATR multiple calculated in Trend “Turtle” Trading?

I have been reading a few books about trend trading and the famed "Turtle" strategy. One concept that is evading me is how the ATR multiple for risk is calculated. I think I understand how to make the calculation after you have the multiple and how this gives you 'leverage'. If the ATR multiple is 7.5 then you divide the multiple by your risk percentage (e.g. 2% of account/7.5) and buy the resulting number of shares - correct?

But how is the multiple even calculated? I read that the "Turtles" only used a multiple of 2x. But other books I've read seem to use arbitrary numbers like 2.5, 4.5, 7.5. How is this calculated?

The Turtle risk management dictated their stops, their additions to positions, and their equalization of risk across their portfolios. For example, a corn futures contract (a standard corn contract is worth \$50 per cent) with an “N” of 7 cents has a risk of \$350 (7 cents X \$50). If the Turtles received a corn breakout signal (using a 2N stop), they would have had a “contract risk” of \$350 X 2, or \$700.

Covel, Michael W. (2009-10-13). The Complete TurtleTrader (p. 83). HarperCollins. Kindle Edition.

I don't fully understand this explanation either. Who calculates the N of 7 cents? How was that number decided over a multiple of 2?