Conveyance calculation

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Conveyance calculation

jpet6502
Hi everybody.
I'm new to the forum and don't know if this has been answered before.
I'm using Hec-Ras to solve one of the examples, in particular Critical Creek (Critcrek.prj).
I can't understand how is conveyance calculated for the left overbank.
While it is calculated correctly for the main channel and right overbanks as K=1.486/n*A*R^(2/3), this doesn't hold for the left overbank.
This continues for all 12 sections but the maximum error is for section 2 (6.26%).
Here are the numbers for the second section as copied from the table:

Area left             2086.7
Area channel         236.92
Area right                0
W.Perim left          641.54
W.Perim channel      48.61
W.Perim right            0
H.Radius left             3.25264  OK
H.Radius channel       4.8738    OK
H.Radius right           0.66199   OK

Conveyance left        72617   (1.486/0.1*2086.7*3.25264^(2/3)=68072.2)  
             Differece =  4544.8   WHY ????
Conveyance channel  25300    (1.486/0.04*236.92*4.8738^(2/3)=25301)  OK
Conveyance right            0     (1.486/0.1*0*0^(2/3)=0) OK