Rookie Mistake

Two targets on one instant, split between mismatched effects, is what lifts this above a plain shrink spell. The -2/-0 half kills nothing outright: it drains power, so an attacker deals less on connection and a blocker trades down instead of trading even. The +0/+2 half hardens whatever creature you point it at, and nothing in the text requires the two targets share a controller. Point the +0/+2 at your own blocker and the -2/-0 at the incoming attacker, and it reads as one clean answer to a swing: shave two off the aggressor's power while padding your defender's toughness, and an attack that looked lethal becomes a chump that walks away. Split them the other way (buff your attacker's toughness, weaken theirs) and you push a creature through a block it would otherwise have died to. The charm is that the numbers are fixed but the geometry is not: two independent targets on an asymmetric split mean the caster decides at cast time whether this is a defensive save, a combat cheat, or an early answer to an aggressive drop by handing a small blocker enough toughness to survive the exchange. As blue combat interaction the raw figures are deliberately modest; the value is in aiming two halves wherever the board needs them, which is what earns the single mana.