(declare (debug 0))

[Stephen Gildea]

The node Instrumenting Macro Calls in edebug.texi recommends declaring
  (debug 0)
to specify that none of the macro's arguments should be instrumented.
But all examples I could find in Emacs code use (debug nil) for this.

Which is it, 0 or nil?

If 0 is the preferred specification, should the documentation say what
other integers mean?