Topic: cycle time of miner modules = x/(1+bonus)
EDIT: modified so people can easily calculate their cycle time.
* Thanks to Recognizer for finding the solution *
I use a Standard small miner module (default cycle time): 18s. The cycle time according to the information window (equipped with Stermonit charges) is: 14.63s.
When mining Stermonit, I use 20 charges in approximately 292 seconds and thus the cycle time is approx 14.60s. = no problem/bug here.
With normal percentage calculation, this would be a decrease of (1 - 14.63/18) ~ 18.72%.
Now my bonuses with an effect on the cycle time of miner modules:
Argano cycle time bonus 5%
basic robotics 4 (bonus of 4*5% = 20%)
basic intensive mining 3 (bonus of 3*1% = 3%)
advanced extensive mining 0 (requires basic 4)
expert intensive mining 0 (requires advanced 5)
intensive stermonit mining 0 (requires basic 5)
What one might expect is a cycle time of 18-23% = 18*(1-0,23) = 13,86.
But as it turns out, the formula being used is as follows:
cycle-time = base-time / (1 + bonus)
e.g. cycle-time = 18 / 1.23 ~ 14.63