If SweetSpot determines that your little one will likely be tired before the “day end” time that you set in the SweetSpot Settings, that SweetSpot time will be labeled as a nap. If this is happening a lot, consider whether the “day end” time should be adjusted, or whether your child is in a nap transition period such that the number of naps may vary from day to day.
See the FAQ “How do I adjust my SweetSpot Settings” if you’re not sure where to do this.