It must be QA. Some of the ones sold are NOT accurate. You two are fortunate that yours are true when compared with your free weights. This WSB Aaron caught:

measured barely 30lbs on the beach (fluctuating between 27 and 30lbs) using that scale, brand new. We knew this had to be wrong and weighed it at Malibu kayaks, using a better model scale it went 37lbs. 6 oz.
Our bad experience with this scale has already been verified with other users. Glad you guys have ones that work properly.
In fact, most everyone agrees Julie's yellowtail:

which weighed 32lbs. on the same scale, looked closer to 40lbs. and Aaron's 29lb yellowtail:

probably closer to 35lb.
We want to buy a better scale, suggestions anyone?