The .NUMBER APPENDIX command allows you to specify an identifying
    letter with which a sequence of appendixes will begin. The next
    .APPENDIX command starts the sequence. Subsequent .APPENDIX
    commands cause appendixes to be lettered in alphabetic order.
    See also .DISPLAY APPENDIX.

    Format

      .NUMBER APPENDIX  [[+/-]n]

    Abreviated format

      .NMAX  [[+/-]n]