"Spec. air mass" and "Spec. air adaption"
 

In the service manual, in addition to the mass air flow specification, there is "Spec. air mass" and "Spec. air adaption." The mass air flow spec is 15 kg/h and the spec. air mass figure is pretty close to that at 15.5 kg/h.

They're measurable in Durametric. On my '99, while the mass air flow floats around 15 kg/h, the spec. air mass is steady at 13 kg/h, and so is the spec. air adaption at -2 kg/h.

What are these two additional figures and how are they different from mass air flow?

Is anybody else's spec air mass and spec air adaption off? I'm wondering if it's just one of those things that's never to that baseline and not a big deal.