The display of a 24-hour digital clock shows hours and minutes in the format XX:XX. For what fraction of a day is at least one 2 displayed on this clock?
"During what fraction of the day does it display at least one '2'?" So, at least one '2' means that if it shows at least one '2', it's included, otherwise, it isn't.
What it means is if there is a 2 displayed anywhere on the clock it counts