Cost falls as quantity grows

A cost from an Add Costs node gets cheaper in total as more is shipped, at the steps the message names. This is a warning: the solve uses the cost as written. It is often a step's Total cost at From entered as an amount added to the step before.

What to do

Total cost at From is the whole cost at that quantity, so it is normally at least what the previous step reaches at its To. Correct the steps in the Add Costs node, or leave them if a larger quantity really costs less in total.

Where it comes from

Shown by Network Optimization. It is one of the messages about a node.