While I have concerns with how Deanna handled this (I agree that it sets a bad example for her daughter), in a strictly boolean sense, the sign was indeed misleading. It may arguably be "open to interpretation", for the simple reason that it follows *somewhat accepted* grammatic conventions, rather than a strict boolean interpretation--but the onus should be on the retailer to not post signage that is "open to interpretation".

It's an unfortunate reality that we have to be vigilant in double-checking prices (for example, I often find merchandise misplaced or mismarked). That reality is only compounded when we blindly accept and even defend retailers' sloppy merchandising and signage.