[m3047]

If I can light a cigar and talk like Columbo for a minute, the thing I can't get out of my mind is that a competent professional would do something like this:

  FILL IN THE BLANKS:
  ___-XXX-XX09 [don't know]
  XXX-_X_-3X4X [don't know]
  XXX-XXX-01__ [don't know]
  2XX-___-XX8X [don't know]

because a competent professional's default is to preserve as much entropy as possible for both parties. The "don't know" button is present because one or more of the challenges is something not known to the challengee.

If a competent professional sets it up blind (no information whatsoever disclosed to the challengee) to capture the entire entered telephone number that is because there is an explicit desire to capture all of the entered data.