Your recommended eating window is when your body is most ready for food. Your body’s metabolism changes throughout the day and one of the main controls for how it changes are your circadian rhythms. When you wake, get bright light or no light has an impact on your best timings for food.
Try to keep most of your calorie intake during your recommended eating window in Arcashift. On shift schedules especially, your eating window may not overlap much with when you are awake. You should eat when you feel hungry, but try to consume the majority of your calories during your eating window if possible.