That green triangle is primary retracement. The tradebox is following Risk:Reward = 1:2.
But the best way to put the trade box is to use Fibonacci. You can use any Fibonacci tool but in this example “Trend Based Fibonacci Extension” is used to see how much BC has been extended towards D in terms of Fibonacci.
As you see our entry is at 0.786
It is rightly consolidating on 1.618 level but one could have take profit or partial profit at 1.618 levels instead of 2.618.