Shortcut to start sleep timer with default duration?

[iPodVT]

I want to add an item to my shortcuts menu that will turn on the sleep timer for the amount of time that is currently set as the default duration.  But the 'data' field in the shortcut specification calls for "sleep X", where X is the number of minutes from 1 to 300 for the timer to run, or 0 to cancel the currently running timer.  Does anyone here know of a way I can specify that the shortcut should use the default duration?

FYI:  I tried "-1" but that was interpreted the same as "0" and cancelled the timer.  Then I tried a number greater than "300", specifically "600", but that started the timer at 10hrs, so I guess the "300" in the spec is not the real upper limit.  I also tried not specifying a number but that resulted in the shortcut being omitted from the shortcuts menu.

Thanks.