Yes, ALWAYS read the description and contact the seller if you have ANY questions, not just on EBay but if you buy from an online QS too.
The amounts do vary by collection size and some jelly rolls duplicate prints too. The name "jelly roll" is more about how the shape of the 2 1/2" strips roll up and resemble the food product, not by any number contained.
I feel your disappointment and this is just one of those things that we (and our wallets) learn a lot from. I too have bought off EBay and not gotten what I thought. As to be expected, I didn't read the description thoroughly enough. Up side, it was still beautiful fabric that was a welcomed addition to my stash.
Hope you'll hunt down exactly what you need to finish your project. I know we all want to see it!