At the top you should have your on layout start so it should be
on layout start->(subevent)Audio is playing (Audio Tag)->(Action)Audio Stop(AUDIO Tag)
That has to be before the play audio and the way to but it at the bottom of the on layout start event is create a blank subevent below it
Also as a side note::
Just sharing a personal preference The 'On Start of Layout' should be the first event in a eventsheet; IMO because everything executes in order that you have it setup. So nothing should be running before 'On Start of Layout'. Events should be place in level of importance and being that 'On Start of Layout' setup the level it should be number#1