Visual Entertainment and Technologies Forum

When ordering 60 vehicles per year the game indicates you'll get a delivery of 6 each month:
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I believe this has been an issue since contracts were implemented in the game. The divisor is not exactly 12, since that can cause rounding issues that would result in breach of contract. Instead the system is something X/11.9 +1 guaranteeing you make enough units within 12 months. Normally this works fine, but fails when the months are divisible by 12.

I can't throw a lot of time on searching the Steam forums, but you should find why this was implemented on there around 2014-2015.