I see that Maretron’s DSM150, DSM200, and DSM250 displays have a DST100 configuration setting called "Clear Speed Calibration:"; what is this?

Maretron’s DSM200 and DSM250 displays have a DST100 configuration setting called "Clear Speed Calibration:", which is used wipe out or clear the multiplier used by the displays to adjust the Speed Through Water (STW) value coming from a DST100.