The amount added is not in %, it addad pulse width so your 40 is an added 40ms pulse width
Yes i too realised that the duration was in seconds, but i remember cliff or dnb saying something before i realised this, so at least i had it in the back of my mind.
In comparison, the addad PW values i am using at 1.2s duration are 0.1, 0.2, 0.7 and 3.0, so it realy does depend on the required fuel calculation