Kudos to the OP for finding the error.
As far as "2 hours" is concerned...
That is the MOST it can stay down.
Let us say you just porked some ord at an enemy field.
IF the Ammo strat is at 0% (i.e. destroyed) and the City strat is also 0% then that ord you destroyed will stay down for 2 hours.
This can be shortened by resupplying. Each batch takes 15 min. off the resupply time. So 8 guys with m3's that have Field Supplies could bring back the ord you porked in one trip. 4 m3's it will stay down one hour, etc, etc..
(does this all still happen btw? I never pay attention to Strat anymore)