mtg card explained How to Play Magic: The Gathering (For Beginners) Magic: the Gathering Basic Definitions:
Description
The number on the right is the toughness of the creature

(It cant be the target of spells or abilities.) Might of ancient wood and stone, Into spirit, flesh, and bone. Illustrated by Pete Venters Standard Not Legal Alchemy Not Legal Pioneer Not Legal Historic Not Legal Modern Legal Brawl Not Legal Legacy Legal Comp

Channel [Pay Life, Cast Anything] Channel is one of the most infamous green spells ever printed
In other words, the upkeep cost is "cumulative", hence the name