SCCM 2007 BDP Status Exact Meaning

What are exact meaning of BDP Status below (0,1,2,3,4)

BDP_Status

WhenStatus= 0 Then'Healthy' 

   WhenStatus= 1 Then'Warning' 

   WhenStatus= 2 AND AvailabilityState = 3 Then'Critical' 

   WhenStatus= 2 AND AvailabilityState = 4 Then'Very_Critical'  

Fazal(MCTS)