Does SweetSpot indicate the time we should start getting ready to sleep, or when my child should already be asleep?

For most children, you'll want to aim to be asleep by the SweetSpot time. So if it typically takes 15 minutes to get ready to sleep and then 15 minutes to fall asleep, you’ll want to start that routine 30 minutes before your SweetSpot time.

You can set up a phone notification to get alerted “x minutes” before your SweetSpot times by going to Child  --> SweetSpot Settings® and turning on the SweetSpot reminder.