It’s no more than 3 items per transaction, of which no more than 2 of the same item. Then no more than 6 items in 4 weeks / a month. And in total no more than 12 a year.
I recently bought more than 6 a month and order was cancelled although I didn’t call to confirm that this was why I just assume. Anything you return or exchange still counts as a purchase unfortunately. However I know some people who go into stores to buy over the purchase limit and have no issues if the SA sees you’re clearly buying it for yourself.
I also wonder about making a separate account to buy more items if you’re over your limit and if they find out and what happens.... I’m too scared to try haha. Anyway I think what I wrote is correct but others may be able to correct me