on All in One latest edition page 384, the design of strap footings is asked.

In addition to axial loads, the also calculated a moment based on the axial load of one footing times distance to the other footing and borught it as a moment to second footing. and based on that moment, from moment arm, they calculated an additional axial load on first footing. then they deducted that transferred axial load from the first footing

sounds confusing but here is my question. how do we know from which footing to which footing to transfer the load? i mean why did we add axial load to footing 2 and deducted it from 1 and not the opposite