Take for example you shortlisted a stock ”X” for buying. The stock would have moved up to some extent by 9:30 AM and the stochastics indicator is in the overbought region.
You should never buy at this point – Chances of profit booking is high in the overbought region and entering at this point you may end up in loss.
So, to be on the safer side you wait for the stochastic indicator to come down a bit and enter when you get the bug signal for the first time.