It works like that :
You summon your grounding totem :
a) If your totem doesnt redirect a spell, nothing happens.
b) If your totem redirects a spell, the CD of Ascendance is decreased by 12s.
Same story for other totems.
This effect (CD of Ascendance decreased by 12s) can just happen 5 times until you use Ascendance so finally if you use correctly your totems Ascendance has a 2min CD instead of 3 (because 5-12=60s=1min and 3-1=2min).
And keep in mind it is just numbers that can be changed for balancing !