This estimator assumes that the motor can draw the required amps, so to get the estimated rof a good battery and wiring is needed. See the electrical guide for details about how to improve your gun's electrical system.
Also keep in mind that most motors are different, so some motors may not perform as well as the estimation. Some motors (especialy used ones) may require motor maitenance to perform optimaly.
The gearbox load is also an estimation, so depending on all the different parts in your gearbox it may be differen. The most common problem adding load to the gearbox is bad Shimming.
Cylinder / Barrel - Ratio
2.13 : 1
The cylinder volume ratio affects both the velosity if the bb, and the acuracy of a gun. For more information se the Volume Ratio guide that explains the details.