What does the hotel double breakfast mean?

Just stay for one night and provide two breakfasts the next morning, which is usually self-help and free.

Breakfast not included: the room rate reserved by the representative does not include breakfast. If you need to use it, you need to consume it separately.

Breakfast included: it means that the room reservation fee includes one breakfast.

Including two breakfasts: the room rate reserved by the representative includes breakfast for two people, which can be eaten free of charge during the stay.