Question about IPFW (NoCat under FBSD)

Dear list,

The following questions addresses for NoCat installed under FBSD

Our installation goes into the same box for different functions (auth and 
gateway).

Within gateway function under, we found bin/initialize.fw file that supposed 
to be called for every startup.

Let say an interface IP is 192.169.1.131 and DHCP range is 192.168.1.194-254.

The following lines are the snipped of bin/initialize.fw file
# Others
${IPFW} add 60100 queue 3 all from any to any in                 // line A
${IPFW} add 60100 queue 4 all from any to any out                // line B
${IPFW} add 60110 skipto 61000 all from any to any               // line C
${IPFW} queue 3 config mask src-ip 0xffffffff pipe 3 weight 75   // line D
${IPFW} queue 4 config mask dst-ip 0xffffffff pipe 4 weight 100  // line E
${IPFW} pipe 3 config bw 128Kbit/s                               // line F
${IPFW} pipe 4 config bw 512Kbit/s                               // line G

Questions :
+ why line A and line B using the same command number with different pipe and 
different functions ? Seems both command working half duplex. Is it right ?
+ what line C for ?
+ what line D and E means and for ?
+ line F and G seems for bandwidth limiting. But how this command work ? For 
line G, is it 512K from interface card sharing for the whole DHCP addresses 
or 512K from interface card to each hosts within DHCP addresses ?

TIA

PD