As the name suggest this is a scaling policy that you define at specific schedules / intervals. The scaling is not a reaction to something that happened, but an action that you take to prevent your instances to not perform in the way you'd like.

If you know that every day at lunch time you have a peak in usages of your application, you could set up a Scheduled Scaling for 11:45 to bring your instances to a certain number ( desired / min and max running instances ).