MX 5 NA 1.9

A question, even if the MX 5 is undoubtedly built for cruising, why is the 131 hp with 197 given and the 116 hp with 195? It would have to run a little over 200, like 203 approx. or changes the CW value? The values were measured with closed cover and closed headlights or? for the extra power only 2 kmh is very strange, even if it doesn’t matter as I said, because you drive a little faster with it at most a few minutes and as a journey Speed 80-100 preferred