If there's an auto sell at 20, max 200 bushels, and a manual sell at 20, for another 200 bushels, then a caravan SHOULD be able to purchase all 400 bushels, as long as the caravan has sufficient gold and was told to buy at 20.
Is this the way it will work, or will two caravans need to be sent?
That's not the way automatic offers work; they're not "for X bushels" but "as long as the warehouse has at least Y bushels."
That said, you are correct (I believe); a caravan that uses up part of its funds buying from a manual offer will not then go on to check if there is an automatic offer to finish spending its money. And similarly with a caravan selling food.
I think. I always have a hard time remembering which bits of the food & trade system I've finished and which I haven't
If you report a bug on this subject, that will help me remember to check on it, and fix it if it needs fixing.
