What's your BTG level ? With what you said I think it's level 12.
In this case a production gives 50+19% BTG bonus = 59.5, rounded up to 60. However if you collect 3 productions it shows 179 because it's actually 3×59.5 = 178.5, rounded up to 179.
(I'm not sure of what I said here. My own BTG is actually level 6, which gives an integer 56 draft laws per hour. However, I already collected things like 7031 treants from a production of 5 squads in barracks, probably due to a non-integer training squad size due to Simia, which is rounded after multiplication by 5 as well.)