Maybe they targetted other people who have bought registered stock but aren't members, in the hope of recruiting more. Or maybe potential advertisers? Sorry, but don't know anything about either of you, so have no idea what pigs you have. Just a thought.
The other thought (purely cynical, but having worked as a journalist for almost 30 years, and knowing the way newspapers and magazines work), in order to be able to say they have a circulation or readership (two different things) of xx000, they have to actually distribute sufficient copies.
This is important when pitching to potential advertisers, e.g. if they were trying to get a big feed manufacturer on board, the big carrot to dangle would be saying that the magazine would reach xx000 potential customers. But, of course, just SAYING that would be dishonest, so some publications will distribute free copies (at a cost of pennies to them) in order to achieve the circulation/readership figures they want.
For what it's worth, I thought it was a pretty good stab at a first magazine - albeit a little basic for the more experienced BPA members. It's a difficult line to tread - choice between over-simplifying or talking over people's heads. Be interesting to see how it develops. Always good to see a new publication launched.
Enjoy your free magazines.