The charger from the Forerunner 620 is not directly confirmed as compatible with the Forerunner 255 (46 mm). Garmin recommends using the supplied charging cable to charge the Forerunner 255, which is specially designed for the charging port of the watch with the Garmin triangle symbol.

Since Garmin provides a separate charging cable with a specific connector design for the Forerunner 255, it is unlikely that the charger from the Forerunner 620 will fit easily or work optimally. For safe and correct charging, the original or an expressly compatible charging cable should be used.

In summary: The Forerunner 620 charger is not labelled as compatible with the Forerunner 255, so the original Forerunner 255 charging accessories should be used.