its the “highest common divisor” frequency for the large tone frequencies in your setup (including divided down frequencies).
There is no “beat” in analysis statement. Also see “spectre -h pss”.
You should not use term “beat” in PSS setting. Expression of “beat” is not proper.
Fundamental frequency of PSS is not beat frequency.
I can’t understand why Cadence has kept to use this expression of “beat” in PSS’s setting UI.