It should just return a precision estimate along with the data. Here's what the ancient (from january 1996) standard for "location" records in the DNS specifies, which in my view is very sensible: https://tools.ietf.org/html/rfc1876

    SIZE The diameter of a sphere enclosing the described entity, in
    centimeters, expressed as a pair of four-bit unsigned integers,
    each ranging from zero to nine, with the most significant four bits
    representing the base and the second number representing the power of
    ten by which to multiply the base. This allows sizes from 0e0 (<1cm) to
    9e9 (90,000km) to be expressed. This representation was chosen such that
    the hexadecimal representation can be read by eye; 0x15 = 1e5. Four-bit
    values greater than 9 are undefined, as are values with a base of zero
    and a non-zero exponent.

    HORIZ PRE The horizontal precision of the data, in centimeters,
    expressed using the same representation as SIZE.  This is
    the diameter of the horizontal "circle of error", rather
    than a "plus or minus" value.  (This was chosen to match
    the interpretation of SIZE; to get a "plus or minus" value,
    divide by 2.)

...so, for a point "somewhere" in the united states, I'd reckon that SIZE=1·10⁰m (1 times 10^0=1m) and HORIZ (and VERT) PRE set to 5·10⁶m (5 times 10^6=5000km) would be a sane choice.

(measuring on google maps, the united states seem to measure about 4500km from east- to west-coast)