Beware that at Canadian Tire, where the chains are on display, people swap more expensive chains into packages and bags labelled for cheaper chains. This way they get a discount. Two years ago every bag in the bin for my size had a different size chain in the bag, and none of them were the right size. The staff were totally unhelpful in resolving this, and so I ended up buying a set that was the wrong size.
The problem arises that if you buy chains and find they are the wrong size, even if you try them in Canadian Tire's parking lot, they will not take them back. It took me an hour to convince them to take mine back.
Two suggestions to lower your risk:
At least some chains have a few numbers stamped somewhere on them, that correspond to part of the code on the outside of the package. This is true for the best chains, the Diamond pattern ones.
Second, you might consider taking your spare tire into the store with you to fit the chains. If the staff challenges you, just explain that the combination of their contaminated stock and strict return policies make it necessary.
I ended up buying a set someone didn't need, never used, for about 60% of the new price.
Meet you at DYE-II?