forward metric ospf E2

i found a strange forward metric in the ospf "show ip route 192.168.1.0", but there is lot of meaning in to it
how to find the better router between two e2 routes



lo--->r1-(rip)--->r2--(ospf)--->r3

ospf area 10

lo:  192.168.1.1/24

r2:

do sh ip int bri
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            unassigned      YES unset  administratively down down  
FastEthernet0/1            unassigned      YES unset  administratively down down  
Serial1/0                  192.168.2.2     YES manual up                    up    
Serial1/1                  10.1.1.1        YES manual up                    up    


r3:

O E1 192.168.1.0/24 [110/84] via 10.1.1.1, 00:00:18, Serial1/0
O E2 192.168.2.0/24 [110/20] via 10.1.1.1, 00:00:18, Serial1/0


r3(config-router)#do sh ip route 192.168.1.0
Routing entry for 192.168.1.0/24
  Known via "ospf 10", distance 110, metric 84, type extern 1

(64+20=84 ::  64 is forward metric + 20 default)

r3(config-router)#do sh ip route 192.168.2.0 ---->E2
Routing entry for 192.168.2.0/24
  Known via "ospf 10", distance 110, metric 20, type extern 2, forward metric 64

(Forward Metric is actually the cost to reach the ASBR(r2). So the metric 64 is r3 to r2.  )

Why forward metric?

Consider two E2 routers with same metric 20. The best route is determined using the forward metric