If you look at the table of records, you may notice that there are entries with the Accident, and some with Incident in the TYPE column. See below:

The way the system decides is simple. If an Incident/Accident is recorded in the system, and you add one or more injured person(s) to that record, it will become TYPE Accident. If there are no injured persons added, it will become TYPE Incident.

Please Note: The Name of Injured Person on the initial Incident Details tab does not make a record an Accident. For example, if a person was thought to be injured at the first point of reporting, but following an investigation, it was later discovered that they weren't actually injured, the record would actually be an Incident. And so to to clarify - only if a person is added to the Injured Person(s) section would the record become an Accident.