Fir wood production

Anyone else having trouble reconciling their fir wood production chains? I have 3 lvl 2 cutters, and 2 lvl 3 cutters, I have them over-forrested (the production time does not change) and should be producing 322 fir wood logs per hour. Now I only have three lvl 3 coking plants that are using this wood and I've done the math on them and they should take up 298 logs per hour. So I should be seeing a net increase over time of fir wood logs, at around 24 or so per hour. Yet the opposite is true I seem to be loosing around 10-15 logs per hour, anyone else done the math on their buildings and seen anything similar?

I use this website to calculate my production rate: http://ceo-economy.appspot.com/

Remember it takes time for cutters to move from tree to tree so the time may change.

I've run all my own calculations twice and exact same results. I've sat and watched the cutters times and they do not move, again cause I have them over-forrested they always go back to the most convenient tree. Unlike that calculator I'm going off of the total production time, which varies from building to building, some are under two minutes, and others are closer to 2m45s. Just wondering if the game has it's math off a bit here and there and I need to now re-build cutters I've previously torn down to make way for higher tier buildings.

Just a quick disclosure of how my math is working perhaps the problem lies within:

Fir wood cutter lvl 3 overall production time: 2m 6s
60/2.1=28.57142857
28.57142857*3=85.71428571 fir wood logs per hour