This occurs when he must recall which 2 digits apply to which vendor bin and which of the 9 bins corresponds to each of the vendors. After an operator has done this for some time, it will become a part of his long-term memory. Coding the first two digits with letters instead of numbers may reduce the load. Also, make sure each bin is marked with the proper letter code. In addition, the bins could be color coded, so the operator can easily and quickly distinguish one vendor bin from another.
Heuristics is a common tool used in decision making.
Heuristics are rules of thumb that allow humans to make decisions efficiently. When a decision must be made, the mind will generate hypotheses about how to respond to the situation. Since working memory is limited, human can only consider a few possible hypotheses at one time. Heuristics allows us to rely on our experience to only consider the most likely hypotheses and subsequently make a decision quickly. Heuristics are favorable when they allow us to efficiently make the correct decision.