Log files have changed a lot from version 1. You may access v1 log file documentation here.
First, log files are independent of Ninebot variables. They use higher lever concepts as speed, current and not variable 75 or 125. That makes them more independent of the wheel and are the base to support different wheels and protocols.
Second, log files are no longer log files. They are a package that is a directory.
In iOS and OS/X (well, now MacOS once again) nomenclature, packages are directories with an extension in the name and are treated by some utilities (ex.: the Finder) as a file.
There is a package for every file. In it we find a text file for every variable identified by its name plus a .gpx file for the track, a .png file for the sketch of the track and a summary file with minimun, maximum and average of the values of the variables.
All data in the log files in SI units. That means speed is in m/s, distances in meters, voltages in volts, currents in amperes, power in wats, time in seconds, altitude in meters. Temperature is in Celsius degrees and angles in degrees.
Files have an extension of .csv so they can be opened directly from Excel or another spreadsheet.
First line has the file formt version and the start time in seconds from 1970 and variable name.
Next lines are the offset from starting time and the value comma separated. Decimal point is a ".".
Finally, packages are compacted with .zip and sent as .9bz instead of .9bm as just one file. That way transmision is really easy.
An example compresed file may be downloaded here.