duplicate nat rules listed by pfctl

[Gianni]

With the following nat rules pfctl lists duplicate entries, can anyone  
explain why this is?

ext_if = "tun0"
nat on $ext_if from $localnet to any -> ($ext_if)
no nat on $ext_if from $localnet to $vpn_nets

# pfctl -s nat
nat on tun0 inet from 192.168.200.0/24 to any -> (tun0) round-robin
nat on tun0 inet from 192.168.200.0/24 to any -> (tun0) round-robin
no nat on tun0 inet from 192.168.200.0/24 to 192.168.0.0/24
no nat on tun0 inet from 192.168.200.0/24 to 192.168.0.0/24