Why does group priority sometimes indicate the number of paths?

Issue

• On one of the RHEL 5 server, each multipath device is having 2 paths associated with it, and the multipath -ll command output shows that prio parameter is set to 2:

  360060e8005b1c400000abcdef1234d17 dm-25 HP,OPEN-V
  [size=64G][features=1 queue_if_no_path][hwhandler=0][rw]
  \_ round-robin 0 [prio=2][active]
   \_ 0:0:0:19  sdaa  65:160   [active][ready]
   \_ 1:0:0:19  sdau  66:224   [active][ready]
  

• On another RHEL 5 server with 4 paths to the multipath devices, the prio value was set to 4

  360060e8005b1c400000abcdef1234d18 dm-34 HITACHI,OPEN-V
  [size=64G][features=1 queue_if_no_path][hwhandler=0][rw]
  \_ round-robin 0 [prio=4][active]
   \_ 1:0:1:15  sdaby 135:512  [active][ready]
   \_ 0:0:1:15  sdabz 135:528  [active][ready]
   \_ 1:0:0:15  sdbi  67:192   [active][ready]
   \_ 0:0:0:15  sdo   8:224    [active][ready]
  

• How the prio value is calculated? does the prio value in multipath -ll output shows number of path?