Happiness squared.

[fsn]

The two packages were happiness squared. The third package was actually happiness cubed.

But. THERE'S A FOURTH ON THE WAY!!!!! 

I may have to seal up the letterbox or something, and give myself some time to adjust. I don't think I'm ready to go to the fourth power of happiness. I'm not strong enough.  I need the wave of euphoria to fade a little.

It's worse that that. Phalanx is coming. (I'll be the one screaming "where's my bloody Centurion?")  I may have to take spare clothes in case of unfortunate over-excitement accidents.

[Duke Speedy of Leighton]

But 1 squared is 1, one cubed is... One! 

[fsn]

But the happiness from one package is not one. It is a magical, mystical constant - call it "H" - where "H" is a positive real number.  Two packages multiply the happiness quotient i.e. H x H rather than H+H.