Available energy in β+ and β- nuclear reaction

Homework Statement:
Formula demonstration
Relevant Equations:
Ed = [Mn(X) – (Mn(Y) + m(e))] c2
Hi,
I understood that to calculate the available energy in these two reactions could be calculated from Ed = [Mn(X) – (Mn(Y) + m(e))] c^2, but when I have to change use the atoms' mass instead of the nucleons' mass, it gives out two different formulas :
Ed = [M(X) – M (Y)] c2 for β-
Ed = [M(X) – (M(Y) + 2 m(e))].c2 for Ed = [M(X) – (M(Y) + 2 m(e))].c2 for β+
Can someone please explain to me why for β-, the mass of the electron isn't taken into consideration whilst for β+, we'd have to add the mass of two electrons ( when we are using the mass of the atom to calculate ).
Sorry if I have misused any vocabulary, I translated this from french.
Thank you so much for your help!

Please be more specific. What does Ed represent? What two reactions is Ed associated with?
I'm so sorry for that.
Ed represents the available energy. The formula Ed = [Mn(X) – (Mn(Y) + m(e))] c2 uses the mass of the entire atom and is used for β+ and - reaction.
But when only the mass of the nuclei are given, we end up with two different formulas :
Ed = [M(X) – M (Y)] c2 for β-
Ed = [M(X) – (M(Y) + 2 m(e))].c2 for Ed = [M(X) – (M(Y) + 2 m(e))].c2 for β+
I just don't understand what happened to the mass of the electrons in these two reactions.
Thank you!

kuruman