"hey Atticus...Let's get going boys how does this scene rely on the fact that scout fails to understand the situationi am talking about chapter 15...

This is the scene where the mob is at the jail, wanting to
lynch Tom Robinson.  The episode relies on Scout failing to understand it because she
actually clears up the tension by acting in a way that is not really appropriate.  If
she had understood, she would not have acted that
way.

Scout does not understand what the men are trying to
do.  So when she sees Mr. Cunningham, she engages him in small talk, just as she has
been taught to do.  It's not really the time for that, but it works because it makes
Cunningham start to actually think about what he is doing.  This makes him rethink and
he helps to break up the mob.

BTW -- it is Chapter
15.