          The exponent value(s) at which <code>toString</code> returns
            exponential notation.
          </dd>
          <dd>
            If a single number is assigned, the value is the exponent magnitude.
            <br />
            If an array of two numbers is assigned then the first number is the
            negative exponent value at and beneath which exponential notation is
            used, and the second number is the positive exponent value at and
            above which the same.
   