Refers to bed numbers - this does not take account of whether a bed is occupied or unoccupied.
A unit with 10 beds would usually have 3650 available bed days during the year. If one of its 5- bedded areas is closed for 30 days because of ward decoration, there would be 30 x 5 = 150 unavailable bed-days. The available bed-days would now be 3650 -150 = 3500.
European Observatory on Health Systems and Policies. Glossary. 2009.