LUN, when displayed on a watch, most likely indicates "lunes," which is the Spanish word for Monday.
Watches sold internationally often display the day of the week using abbreviations or translations to accommodate different languages. Since the reference mentions clocks sold worldwide, and "LUN" appears on the screen, it strongly suggests that it's the Spanish abbreviation for Monday.
Therefore, in the context of a watch displaying "LUN," it's a concise representation of Monday, catering to users who prefer or are accustomed to the Spanish language setting.
