Milsurp After Hours

I know this expression is from cricket and refers to getting the highest

number of points-like hitting a home run with bases loaded-but could someone make it clearer to this Yank?-

In cricket if the batsman hits the ball to the field boundary without it bouncing it scores six runs (as opposed to four if the ball does bounce.) It takes a mighty blow to achieve this.

The expression "to hit (or knock) someone for six" is therefore used as a metaphor meaning to overcome completely or to take by surprise.

Brian