To determine the carrier wave frequency, just look at fmean which is best approximation of f0.
Ideally the sum of all Sample Intervals should be selected to cover an integer number of modulation periods. This way the positive frequency deviations will compensate the negative deviations during the measurement.
Example: If the modulation frequency is 1 kHz, the Sample Interval 10 μs and N = 1000 will make the Analyzer measure exactly 10 complete modulation cycles. A bad combination of Sample Interval and N would worst case mean that exactly half a modulation cycle is uncompensated for, giving a max. error for a sine modulation of:
f0 – fmean = Δfmax / (sample int.) x N x fmod x π
For very accurate measurements of the carrier wave frequency f0, make an extra measurement session and set Sample Interval as close as possible to an integer number of modulation cycles, and increase the number of samples substantially. A worst case error of half a modulation cycle means far less in a million cycles compared to 10 cycles.