Instance hours come into play when, for example, you run multiple versions of an app that get traffic, multiple instances for handling high load, or if you have

Instance hours come into play when, for example, you run multiple versions of an app that get traffic, multiple instances for handling high load, or if you have separate front- and back-end instances. A typical user only has one instance going at a time, so no more than 24 instance-hours. (Instance hours have been a thing for at least a couple of years.)