See how old the fish is, one minute small and two minutes big. This is very simple. It is cooked food itself and does not need to be heated for a long time. You can heat it for a while, but it's not enough to heat it again. If it is a large pot of fish, it may take 3-5 minutes to heat. It doesn't matter if the setting time is less. You can heat it again. Just keep adding time.