There was a rush to buy the cook drinks and hear more details.
"Always thought he was odd," she told the eagerly listening villagers, after her fourth sherry. "Unfriendly, like. I'm sure if I've offered him a cuppa once, I've offered it a hundred times. Never wanted to mix, he didn't."
Harry potter and the goblet of fire
Instead of if, doesn't it have to be that or something? She's sure that she has offered him a cuppa, quite a lot of times, actually, but he never wanted to join her.
Or if here does mean if, does this sentence mean "if she offered him a cuppa (though she never did), he would have certainly refused it no matter how many times she tries"?
I don't understand this sentence.