According to recent studies on a universe of tens of thousands of graphic patterns (27,000), the chance of a pullback occurring after a support breakout is approximately one in two.
Going into more precise details, these studies indicate that the probability of occurrence of a pullback is 57%. That is, in 57 out of every 100 support breakouts, the price will return to the broken support in the following 30 days (obviously, in 43% of cases, this return will not occur).
In addition, we can estimate that the price will drop during the 5 days after the breakout. Of course, all these data are averages, as you can guess. It does not mean that, after all the support breakouts, the market will drop just for 5 days.