Does anyone know how the Aging Modifier of each covenant fits into the Aging roll?

Covenants start with a base Aging Modifier of 0 (pg.71), and unless I'm missing something, there are no rules, boons or hooks that change this.

Then in the section on Aging (pg. 168-170) we are introduced to a Living Condition Modifier, that for covenants range from +1 to +2.

I just want to know if this is the same as the Aging Modifier from page 71, and if so, why is it not 0. And how can the Aging Modifier change over time?

//I just want to know if this is the same as the Aging Modifier from page 71, ...//
I see no other plausible meaning for the Aging Modifier mentioned on p.71, which is then never referred to again in the entire covenant chapter.

//... and if so, why is it not 0.//
Indeed few Magi will live like the average peasant. So I suggest to consider that Aging Modifier on p.71 as a remnant of an older text version which should have been deleted.

//And how can the Aging Modifier change over time?//
The Living Condition modifier to Aging on ArM5 p.170 is likely influenced by the Urban Hook. It could change if the covenant gains or looses Wealth Boons and Poverty Hooks, or develops into Summer or Winter.
It can also depend on a lot of things which are not formalized in the Covenants chapter, like the area where the covenant is located, a curse laid on it or the drainage of an adjacent bog.
The SG would have to map such effects plausibly to the modifiers, and inform her players. I see no need for utterly precise and exhaustive rules on that subject, though.

Kind regards,

Berengar