As long as it's in the speed band nothing happens no messages, however if it's approaching a speed limit waypoint and it's carrying excess decent speed it's smart enough to say look I'm in path but I'm going to bust the approaching speed limit as I was supposed to be doing 300kts but I've had to do 324kts due to unforecast winds so help me out and give me some drag so I can slow to the 280kts required at the next waypoint"
When it decides to pop this message is I don't know.