Beacon RSSI transform to distance

I trying to turn RSSI transform to distance but i have some question

I read some paper find the formula


I don’t know why use Log

In the class Utils ( SDK version 0.16.0) or class RegionUtils (SDK version 1.0.0+)
you can use methods

computeAccuracy(int rssi, int measuredPower) 
or other computeAccuracy(xxx)