A low brake fluid alert can accompany brake wear or a fluid leak. Adding fluid may change the level without explaining why it dropped. The warning deserves attention even when the vehicle appears to stop normally.
If the brake pedal feels soft, stopping performance changes, or fluid is visibly leaking, stop in a safe place and arrange towing. Do not continue driving to test the brakes. Contact 12th Street Auto Care Center in Sioux Falls to discuss the alert and the symptoms you observed.