"OK, Tom, let's skip all the preliminaries: Why do you think this doesn't mean anything?"

As Rice said this is a summary of past events, opposed to tips and leads in which was currently being investigated. This was the result of past investigations opposed the raw data or summaries of current intel.
In other words, there was a big spike of chatter during the summer; this chatter indicated high possiblity of some kind of terrorist activity- this was being actively investigated.
The president had requested this summary and after working it's way to his desk, got this info at same time a peak in chatter. Imagine the alternative reality of there was no huge spike in chatter in the summer- the report given to President would have be the same- it was historical; it wasn't data developed from the current chatter or data dug up to explain current intel they were actively following.
Analogy: say you were at a baseball game. Who's on Second? What is the score? This is current intel. What the person on second or the pitcher did in past games is historical. You could have gotten this information before going to the game- the President happenned to receive it while he was at the game. It's related in that it's information about baseball games, but it's unrelated to what is happenning now in this game.