A supplemental device for attachment to an injection device is presented having a display; a processor arrangement; a dose dialed detector operable to detect a dose of medicament dialed into an attached injection device; a dose delivery determiner for determining that a dose of medicament has been delivered; a quantity determiner determining a quantity of medicament that has been delivered; and a clock configured to determine a current time. The processor arrangement is configured when the supplemental device is in a default mode to display both a quantity of medicament that was delivered since a last dose and a time elapsed since delivery of the last dose.