In the example above, "too" means "very". Here are some other examples of this:

We're not too happy about the way that he was running things.

A: How's your dad?

B: You know, he's not doing too well. He may need surgery.

"Not too ___" can also have the meaning of "not more than you want":

What a nice day! Not too hot, not too cold.

I like a cake that's not too sweet, you know?

You should be able to tell the difference between these meanings based on the situation.