Use:
SELLCROP(Crop_name[id=id],amount;)
LABEL(x)
NPCSEL(Manor Manager)
NPCDLG(Manor Manager)
DLGSEL(Tally up indigenous product.)
DELAY(1000)
SELLCROP(Red Coba[iD=6542],9999;
King Coba[iD=6547],9999;
Gold Coba[iD=6543],9999;
Desert Coba[iD=6544],9999;
Sea Coba[iD=6545],9999;
Twin Coba[iD=6546],9999;
Blue Coba[iD=6541],9999;
Desert Codran[iD=5090],9999;)
CALL(x)
Test it different way (with 9999 amount or exactly what you get, one crop in one exchange period or more different kind of crop, playing with delay 100ms-1000ms).
First time i exchanged 2 type of seed. One of them was fully exchanged (~2500 unit) to 1-2 castle. SellCrop is always try to exchange with highest prices.
I hope it will help.