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

[986lp]

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?

[986lp]

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.