It's definitely one of the less elegant aspects of the game. It accomplishes it's goal (to make both the level of the casters/sources and the rank of the countering effect matter to the outcome), but it's hard to wrap your head around.
All you need is the Counteract table. Roll a d20 + your spell modifier (like a spell attack). Compare it against the DC you're trying to counteract and the equivalent rank behind that DC.
Like for example if I used Dispel Magic at rank 2:
Failure: I still dispel a rank 1 spell, or a level 1 or level 2 effect.
Success: I dispel any spells rank 3 and below, and effects level 6 and below.
Crit Success: Rank 5 spells and below, and effects level 10 and below.
Comments
Failure: I still dispel a rank 1 spell, or a level 1 or level 2 effect.
Success: I dispel any spells rank 3 and below, and effects level 6 and below.
Crit Success: Rank 5 spells and below, and effects level 10 and below.