From: Utopia Planitia Fleet Yards
According to the manual 1.00.06 page 26:
Convoys and Escorts – Here a player can find all overseas convoys and trades between countries. A player can view, setup, and cancel trades during the game. Trades transfer the selected production and oil every turn to the target trade partner. No more than 25% of a country’s total production and 25% of its stored oil can be traded away. Conquered and owned countries resources only show up on the trade list if they are traveling by naval convoy. Trades travel via undamaged rail or convoy routes.
So, I do understand the 24 max value for Oil export.
But, I do not understand the 39 max value for Production export.
Is the manual correct or is the game correct?
Chancellor Gorkon to Captain James T. Kirk:
You don't trust me, do you? I don't blame you. If there is to be a brave new world, our generation is going to have the hardest time living in it.