I'm mostly unacquainted with the f scaling factor, but this commit seems to make the manual say two slightly different things about it:
> @item f
> @cindex @code{f} unit
> @cindex unit, @code{f}
> -Fractions. Value is 65536.
> +Multiply by 65,535.
...then later:
> +indicator of@tie{}@code{f}, which multiplies its value by 65,536 (but
