"look at the overall?"

Rating: 10/10 (6 June 2010)

The movie is excellent, it keeps you on the edge of your seat. I especially like the scenes where Woodward is meeting with deep throat in the garage dimly lit, it is an exciting touch of conspiracy.
I'm confused by deep throat's comments "look at the overall". What is he talking about? When does looking at the "overall" help woodward and bernstein figure it out? What "overall"?
I also don't understand why deep throat talks in code. Why doesn't he just plainly state what he knows? By talking in code, he only lengthens the conversation and increases the risk of getting caught. I am confused about this as well.