From the guidelines
4. Users should try and give as much information as possible about the clue for example:
a. The Clue itself, for example: “Where is the best place to ask and answer questions?”
b. The number of letters required, for example: (3)/(10)
c. Any letters which have already been worked out in the answer should be presented as: T?E/A??WE?BA?K. Here the “?” represents a missing letter while the “/” represents a space, a space itself is also acceptable. The answer to the clue is, of course, “The AnswerBank.”