The sweetest sounds in the universe - "chai chai"

I often travel in this train and found that seat allocations are different as wriiten here.
01 02 03 - LB MB UB
04 05 06 - SL SM SU
07 08 09
10 11...
more...

12 - LB MB UB
13 14 15 - SL SM SU
16 17 18
19 20 21 - LB MB UB
22 23 24 - SL SM SU
25 26 27
28 29 30 - LB MB UB
31 32 33 - SL SM SU
34 35 36
37 38 39 - LB MB UB
40 41 42 - SL SM SU
43 44 45
46 47 48 - LB MB UB
49 50 51 - SL SM SU
52 53 54
55 56 57 - LB MB UB
58 59 60 - SL SM SU
61 62 63
64 65 66 - LB MB UB
67 68 69 - SL SM SU
70 71 72
73 74 75 - LB MB UB
76 77 78 - SLSM SU