Biens immobiliers- Declaration of occupancy and expected rent

Under the section biens immobiliers at mon espace particulier for impots I am completing some information for an abri. It is on our main property, in the garden and not attached to the house. For the “Declaration of occupancy and expected rent” is the abri considered to be our main property or “vacant property (unfurnished and unoccupied)”?

Size?

14 sq meters