A detailed summary of actions or an event, as in The President wanted to base his reelection campaign on his box score. The term comes from baseball, where since about 1910 it has signified a statistical summary in table form of the essential details of a game. About 1930 it began to be used figuratively, especially by politicians referring to their own record while in office.
In military slang, the number of dead, wounded, or missing in action. For example, Never mind the details of the battle; just give the lieutenant the box score. [c. 1950]