The cam box is just another name for the rocker cover.
There is one on each side of the engine.
To remove the spark plugs you have to insert the plug spanner down through the hole in the cam box to get to the spark plugs.
There is one seal for each spark plug and the seal is above the spark plug so the oil is running down the way.
Any clearer ?
You have pm.
Cheers,
Alex.