Those are not events in the sequence. Those are individual frames. Events in LabVIEW are something completely different. Based on your question it seems you are not completely understanding dataflow. A function/VI will execute when all data on the wires connected to it is present. Dataflow can be used to enforce execution order, but sequence frames can also be used.
In your first frame if you wire a True constant to the Boolean you cannot control when the Boolean is updated since there is no data dependenct between the numeric calculations and the writing of the LED. Thus, if you want to turn on the LED before the first frame then you need to add a frame before the first one where you set the LED, and the same thing at the end.
