I am not that technical sound with ratios and all
I try to buy the ones which I can relate personally and also understand the business in better way.
only reason for rule of selling script getting 20% down is because in one way you can say I am still not mature enough to see loss and also my aim is only to become independence not to be next jhunjhunwala and holding the script if it goes beyond 30-40%
It might seems weird but that’s my understanding and I am aware I might loss lots of good script in this case.