The value is a rating of electrical overcurrent devices that if a fault exceeds it can result in catastrophic failure, or blow up into shrapnel.
To size this value, a short circuit coordination study needs to be done. Along with the impedance of transformers and copper wire due to distances, and voltages and current ratings, will either raise or lower the value equipment must be able to withstand.
This is a serious engineering task sometimes ignored.
Along with this info and additional detail, an Arc Flash study can and should be done.