The shape is a horizontal line with a triangle at the right end.
The shape represents a timeline with an event at the end. It is typically used on ovens and dishwashers to enter a start time. Additionally it has been applied to an oven preheat setting. The thought on this latter usage is a period of time will elapse before the appliance begins its primary function. With a bit more thought, perhaps there is a modification that would better represent preheat.