Electron Affinity Equation

[Nathan Tran 1B]

Hi, so I was wondering if someone could explain why in the Electron Affinity Equation it is Initial minus Final, Eea = (Einitial − Efinal) which is uncommon because equations are usually Final minus Intitial. I know Dr. Lavelle mentioned it in his lecture, but I wasn't able to write down the explanation. Also, could someone explain what the inital energy and final energy would actually be representative of?

[zackdouchy]

Although I am not sure of why the equation is arranged like that, I do know that the initial and final states simply represent the energy state of the atom at those given times.