When predicting the end of a 12345 wave, it's only important draw the channel line touching the ends of wave 1 and 3. Wave 5 is expected to end when it touches this channel line. It is confirmed when it exits the top of the channel, but by that time the price of BTC will be hundreds of dollars above the bottom so it's kinda too late to buy the bottom. It's better to set a buy order where Subwave 5 is expected to touch the channel, and then wait for confirmation and be ready to sell if it's invalidated.
It's only a prediction based on probability though - nothing is set in stone - so stay cautious.