Currently using a trial of BetAngel, and I am having trouble to get my head around some (probably) simple things.
I am dabbling a bit to get to know the program, and I am trying the example of the BetAngel channel on YouTube, on the under/over 2.5 market.
Now, I am having trouble understanding something. Say I back the under 2.5 at 1.8, and also put a lay bet in at say 1.5, why would I need to green up?
To explain my train of thought...there are only two possible outcomes, it is either under or over. Does the lay bet on the under not cover all the possible outcomes? Or is it indeed necessary to green up? If so, can someboy explain to me why? I was never that much of a math genius I am afraid.

Thanks in advance for answering my undoubtedly silly question!