Indulgent Consumer

I've noticed that my trade history has been a bit wonky for a while now. I have many trades I've completed from 2014 lone, but it still shows some 2013 trades instead. This isn't really a bit or immediate issue that has to be addressed, since it hasn't really caused me any problems yet, but I was just curious about it.

That aside, why do we get capped at 13 trade slots anyways? If anyone else can answer that for me as well.