J.K.
This is the link for eligible SNAP food items:
http://www.fns.usda.gov/snap/eligible-food-items
There is no limit as to how many of a particular qualified item you may buy. You're limited only by the dollar amount you get per month. You can buy as much produce as you want, or as much pancake mix as you want, until you run out of funds.
I think the person you were talking with might be confusing SNAP with WIC. WIC is allows only specific types of produce (yes sweet potatos, no russet potatos) and does have limits on how many of certain things you can get.
I can't find an IL list that lists what kind of foods are allowed with WIC, but here is the one for WI. https://www.dhs.wisconsin.gov/publications/p4/p44578.pdf
And this is the page saying how much of each thing you can get at each WIC level:
http://www.fns.usda.gov/wic/wic-food-packages-maximum-mon...