The hr2 file is generated when you enable the option for extended velocity range in the instrument configuration. We extend the velocity range by placing a single measurement cell 1/3 into the profile. The hr2 file shows the measured data in this cell. Since we then also use a shorter lag, this cell gives us the velocity at this point with a factor 3 higher velocity range than the regular profile. We then use this velocity to resolve the velocities of the whole profile. You should normally not need to look at the data in the hr2 file since we have used that information already in the profile output. But if you have a data set that looks suspicious, you may want to check that the correlation in the hr2 file to see if there is a problem with the measured data from the second (higher velocity) lag.