Any math majors here? OHC head milled.....

Got a question about an OHC motor that has had the head milled. If the cam sprocket is 109mm in diameter (54.5 radius) and the cam moved 2mm closer to the crank driven by a chain, how many degrees has the cam rotated by being 2mm closer to the crank? It is going to 'roll' down the drive (R) side of the chain CCW and retard the cam timing some degrees. I have an idea how to figure this but I may be dead wrong: 342mm circumference / 360 degrees would give me .95 degrees per mm and if you dropped that sprocket 2mm, would that be 2x.95 or ~1.90 degrees retarded..minus the rotation angle? I would have to cut a new keyway only if this is accurate.