Extremist Couponing

     A small vindication arrived in the mail today-----$20 worth of coupons from Purina, most of which is for free products.  I do not use coupons much any more, and typically only if they're for at least a dollar.
    A week or so ago, I presented a coupon to the cashier at the local market, a dollar off 10 cans of cat food.  The cashier studied the coupon and declared it invalid.  I had bought the carton of 12 cans of the food; he said "they" wanted me to buy the loose cans.  The coupon said 10 cans.  I thought of opening the carton and removing 2 cans, but didn't.  The man at the register appeared new, and evidently afflicted with some kind of psoriasis; I would not want to have been responsible for jeopardizing his job, which is probably on shaky ground anyway. 
    I contacted Purina's Customer Service; they are there to help us.  I explained the situation, and their reply, well within the 48 hour response window, was that coupon redemption policy is at the discretion of each store, and recommended I take the coupon to another store. 
  Really?  Drive to different stores until I find one that happens to agree with the wording  I'm reading?  That would be unwieldy and humiliating, I told them.  And stupid, I didn't tell them.  Instead, I said that my issue was not with the store, but with the wording in the coupon, and suggested editing so that the meaning would be clear, and universally understood. The cashier thought that he was following the dictates of  the great god Purina. 
    So, after jumping the line of the first level of customer service reps, I was thanked for bringing up the issue, and told that they were going to work on it. (Which most likely won't happen)  And send me some coupons as a token of their appreciation. (Which they did.)