The ECU is always aiming for 14.7:1 AFR in closed-loop, I'm not 100% sure, but this *might* be in the source code rather than a calibratable map - certainly it's not a map address I'm aware of.
The upswing/downswing maps define the correction limits (correction of fuelling up/down respectively) of the closed-loop lambda control. Without these limits you can face two problems:
a) Instability - the corrections the software make constantly over or under-shoots the target 14.7:1 AFR, so wobbles all over the place.
b) Dangerous lean AFRs on lambda failure - a faulty lambda means incorrectly applied fuelling corrections. Thus you need to limit the amount of correction that can be applied, so to avoid running so rich the sump fills with fuel or so lean it melts the engine, when the lambda's failed.
I think the decay dictates where the ECU transitions from closed to open-loop control, as at higher rpm and loads it's not in closed-loop - even if the WOT switch is not active.