Generally if you are riding around (i.e. NOT in the pens) warming up before an event, and then you select the ‘Join Event’ button in the bottom left of the screen, the activity you are in is saved as a separate ride from the event, while the miles ridden AFTER the event (presuming you stay in the same world) are counted as additional miles in the event. So, check your activity log to see if you have a separate ride before the event.