Scatter plot and RMS

Hi all
I have a question. Feflow 6.1 calculates RMS in the scatter plot window. How its calculated?. the observed times and simulated times are different, felfow interpolate de simulated results to get a result in the observed time??
Thanks

RMS = (sum of (computed - observation)^2) / (number of observations)
STDEV = (sum of (computed - observation)^2) / (number of observations - 1)

It's not just FEFLOW 6.1 that calculates RMS this way.  ;D