Before converting the array into the Dynamic Data type, convert it into a waveform type. Feed the data into the Y element of the waveform cluster and enter the inverse of the sampling rate into the dt element of the waveform cluster. Feed the waveform data into they Covert to Dynamic Data and change the properties of it to accept a single 1D waveform. Your frequency info will then appear in the FFT.
Looking at your data, if this sine wave is at 100 Hz then it is not sampled at 800 Hz. It is sampled at a higher rate.
Randall Pursley