vanakkam .. long time no see ..
would you explain by example ..?
he says, to arrive at position sizing he tried two approaches one flop another good.
In flop version: he calculated the number of lots to be traded first and then amount to be risked in that trade and set his SL.
This is flop (in my opinion) bcoz he forced his idea of how much volatility market should have as per his plan. As we all know hardly market takes our orders, market is always the boss.
In his second good version:
He respected the market first, arrived a decent safe volatility distance before market hits your SL. He took this distance as safe SL distance and calculated the amount he can risk per trade, after this two steps now he can get his proper lot size which he can trade safely!