docs: public final Timestamp adjustMillis(long amount) {
          if (amount == 0) return this;
          Timestamp ts = addMillisForPrecision(amount, _precision, false);
          //ts._precision = _precision;
          ts.clearUnusedPrecision();
          if (ts._precision.includes(Precision.SECOND)) {
              // Maintain the same amount of fractional precision.
              if (_fraction == null) {
                  ts._fraction = null;
              } else {
                  // Truncate the result only if it exceeds the fractional precision of the original.
                  if (ts._fraction.scale() > _fraction.scale()) {
                      ts._fraction = ts._fraction.setScale(_fraction.scale(), RoundingMode.FLOOR);
                  }
              }
          }
          return ts;
      }