From my XLT Book. Your number range will be different, but the basic use should be the same.
2. S.A.T. Speed
Self-Adjusting Threshold (auto-tune) smooths the
THRESHOLD, OFF (0), or ON (1-10).
Without S.A.T. SPEED (a setting of 0), changes in
the ground (and the passage of time) will tend to
produce changes in the THRESHOLD sound. The
TRIGGER will have to be squeezed and released
repeatedly to maintain the THRESHOLD. This is
particularly noticeable in non-discriminate modes,
although S.A.T. SPEED will also tend to add
stability to discriminate modes. S.A.T. SPEEDs 1
through 10 will automatically correct for such
THRESHOLD changes.
S.A.T. (auto-tune) is a feature that has been used
on metal detectors dating back to the 1970's. It
adds a loop-motion requirement to modes which
are ordinarily non-motion. It is also known to
produce some variations in the responses to hot
rocks (rocks more mineralized than the surrounding
ground) which change with different speed
selections.
Only enough S.A.T. SPEED required to maintain
stability is recommended. Typically normal coin
searching requires slower (lower number) speeds,
beach hunting and relic hunting require slightly
faster speeds (higher numbers), and prospecting
requires the fastest settings (highest numbers).