The limitation is per product category (e.g. books = 1 category, software = 1 category), the maximum number of items is that Amazon returns in response to a single query.I believe this number is 10.
So the max you could display is 10 per category, or if you had 16 categories (for example), 10X16 = 160 total products.
I know that I haven't explained this too well, so there is another explanation here (I've just spotted couple of typos in it, but still makes sense I think)
Here
http://www.scriptrocket.com/faq.php
Under
"Can I configure the number of results returned from Amazon?"
Hope this helps
