So, it just means your AP current is larger. Depending on the electronic states, this can certainly happen. And yes, I would agree with you that the second version of the formula makes more sense in this case. In the end, the "TMR" is just a figure of merit, the real results of your calculation are Iapc and Ipc, so as long as you present those clearly, and the method used to compute the TMR, nothing is "wrong".