Ahmad - Daniele was correct that they're simply read in the order
they're specified on the E1 lines. Here's a working example:

SW 1 0 8
*SW 1 7 8
MM 6 16 12 13 14 27 28
*@ 7 runoff.int
@ 8 trans.int
$ANUM
$TRANSPORT
A1 Demo
A1 Transport
B1 20000 0 0 0 4 0 /
B2 900 0 /
*B3 0 0 0 0
B3 1 0 0 0
C1 0 0
E1 Meter4 '' '' '' 19 0.02 0 0 0 0 0 1 0
E1 Meter3 Meter4 '' '' 19 0.02 0 0 0 0 0 1 0
E1 Meter1 '' '' '' 19 0.05 0 0 0 0 0 1 0
E1 Meter2 Reg003 '' '' 21 0 1.39 0 0 0 0 1 Reg006
E1 Reg006 Meter2 '' '' 19 0 0 0 0 0 0 1 0
E1 Meter5 Reg006 '' '' 19 0 0 0 0 0 0 1 0
E1 Meter6 Reg004 '' '' 19 0 0 0 0 0 0 1 0
E1 Phase4 '' '' '' 19 1.50 0 0 0 0 0 1 0
E1 Meter7 '' '' '' 19 0.15 0 0 0 0 0 1 0
E1 wwtpof wwtp '' '' 19 0 0 0 0 0 0 1 0
E1 CSO2 Reg002 wwtp '' 19 0 0 0 0 0 0 0 0
E1 CSO3 Reg003 Meter2 '' 19 0 0 0 0 0 0 0 0
E1 CSO4 Reg004 '' '' 19 0 0 0 0 0 0 0 0
E1 Reg004 Meter5 Phase4 '' 21 0 100 0 0 0 0 0 Meter6
E1 Reg003 Meter1 Meter3 '' 22 0 0 0 0 0 0 0 0
E1 Reg002 Meter6 Meter7 '' 22 0 0 0 0 0 0 0 0
E1 wwtp Reg002 '' '' 21 0 7.43 0 0 0 0 0 wwtpof
*
G1 2
* Depth Area Volume Not_used
G2 0 6830 0 0
G2 5 6840 34200 0
G2 10 6850 68500 0
G2 11 6870 75570 0
G2 13 6900 88400 0
G3 1.39 0 0
5 10 1.5 CSO3
G5 0
G1 2
* Depth Area Volume Not_used
G2 0 10000 0 0
G2 5 10010 24000 0
G2 10 10020 48000 0
G2 11 10030 55000 0
G2 13 10050 65000 0
G3 7.43 0 0
20 10 1.5 CSO2
G5 0
H1 CSO3 CSO2 wwtpof Reg006
$ENDPROGRAM

Regards,
Mitch Heineman, P.E.
HeinemanMC@CDM.COM <mailto:HeinemanMC@CDM.COM>