Methinks that even the local Canadians, their English has deteriorated significantly, to the point where even when they draft something like a merchandise coupon wording, they can't even make things clear and concise.
This is something I despise on a daily basis, and I'd teach my kids not to follow their foodsteps.
Assuming that you are referring to this said discount coupon; I'd insist that the discount is based on the foodlong price divide by 2 (e.g. 9CAD/2=4.5CAD).
Fault is the lack of clarity RE: based on which pricing. I'd insist to talk to the manager to find clarity on this coupon and the discount.
I do not take the so-called 6CAD for 6" to be fair, if you are to ask me.
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On a slightly different note: I came across (this past summer) similar issue RE: Safeway 4L lucerne milk jug for $2off, max. 2 jugs each. but the wording was confused RE: $2 off per 4L jug, max. 2 jugs ? or $2 off for 2x4L jugs (1off each?)?
So I grabbed the store manager and grilled him on the spot. He turned around and made store-floor announcements (using PA systems) that it's meant to be $2 off each jug, up to a total of 2 jugs per purchase ($4 off total).