If you are talking about options selling, then how can we set a stop loss in it. That's why we are setting a risk-reward ratio of 1:3 and that's our stop loss here.
which means, we are trading in the derivatives market right? here the profit and loss depend upon the premium.
Eg; just imagine if the value of nifty 50 at 10 am is 15000, the corresponding premium is 10 rupees. after a long time, nifty fluctuates and came back again to 15000 but the premium might be less than or greater than 10. So that's why we have set a 1:3 ratio. if you are about to get 1000 as profit, then 3000 will be your maximum loss that you bear and will exit from the trade immediately if we saw the 1:3.