Cloyes 9 key-way timing set

[TVR Beaver]

Got one of these to time my cam in as the adjustable one was loose on the keys and moved every time I nipped the locking bolts.

I was trying for 111.25 and on 2A got it to 110.8 so that’s great and will allow for bedding in.

So the questions more curiosity than anything as in the literature it says moving the crank sprocket one keyway (2 deg) will move the cam 1 deg. On initial setting at zero I got a reading of 112.9 so wanting to advance it 2 deg on the cam I moved it to 4A (they go 0, 2A, 4A, 6A, 8A and the same on R)..
But this gave a cam reading of 108.7? so it had advanced the cam 4 deg and not 2? And having checked 6A this also moved the cam 2 deg?....

So am I doing something wrong here?.. John Eales says he can get to within ½ deg with these and the claim on the box is it will move the cam 1 deg and not 2??...

It’s obviously a 2:1 but advancing 2 deg on the bottom should give 1 get on top.. it’s not accumulative as its fixed?... all very strange?