It's most likely a bug we're currently trying to sort out that involves how the production popup somehow interacts with Sub-Combat categories. I'm not sure why its doing it and it doesn't ALWAYS do so but I'm wondering if it has to do with something that takes place at the point we modify the production speed by CC. Out of curiosity, if you can still see this problem, is there a difference in the amount of rounds it shows it takes to build them?
If you're still able to show the issue, a savegame for analysis would be helpful.