This is an area of English that I consistently have trouble with. Consider the following sentences.

(1) I have a couple of books on my desk.
(2) I have a bunch of books on my desk.
(3) I have a number of books on my desk.
(4) I have a few books on my desk.
(5) I have several books on my desk.
(6) I have many books on my desk.

How many books, give or take, do I have on my desk in each case? 

[digression: one example of how I tend to get these wrong is the following: not long ago, my wife (native speaker of American English) and me were out with a few friends from out of town. At one point I said "[famous landmark] is only two hundred meters from here", to which my wife replied "no, it's more like a a couple hundred meters".]