The size and placement of the angle is completely dependent on the level of intoxication of the shooter. It is also an acquired skill that develops over time and is usually non-existent in those that suck at beer pong and/or drinking.
Note that this is similar to the concept of crosswind correction, an airplane piloting technique referring to the correction needed for a crosswind present during landing.
"Dammit Matt, either start putting in some drunk correction or I'm finding a new partner. I'm carrying this team, asshole."