If I click a production building with modules, the output number is way higher than what it really is.
If there are no modules inserted, the numbers are correct.
Example
Chemical Plant with plastic recipe and 3 level 1 speed modules:
The mod window shows this:
number of machines = 1
2.56/sec coal, 51.2/sec petroleum gas, makes 5.12/sec plastic
But the real calculations is this:
1.6/sec coal, 32/sec petroleum gas, makes 3.2/sec plastic
