He can't know how much and when it will go exactly, just estimate a target.
I think the point of haejin is giving us his analysis to teaches us how he does what he does. Look at his tutorials, buy and reads the books (elliot waves/stock trends analysis) and learn to make TA by yourself. Then you'll know when to go in/out. And if you just follow his advice and get in/out when he says so you will make profit anyway.