Factory ammeter

Honestly, if the ammeter is showing normal charging and discharging I don't worry about it.
If the ammeter is showing excessive charging, then I do a quick check of voltage at the battery.
The reason excessive charging raises a question about voltage regulation is that the battery will attempt to overcharge when supplied with power above 15 Volts.

Of course the other reason there might be higher/longer than normal charging is the battery was heavily discharged. In which case just try to keep the rpms low and get it on a charger as soon as possible.