FFT size:
Number of data points in each FFT block or subseries. The length must be a power of two and cannot exceed the total number of data points.
NOTE: A practical limit for the FFT size is 8192 in a 64 bit application. See also Number of subseries.
Number of frequencies:
Is half of the FFT size
FFT duration:
Gives the length of the FFT analysis in seconds
Frequency interval:
The difference between two discrete adjacent frequencies. If manually changed, the value is automatically adjusted to the nearest possible value (function of time step and FFT size)