I've noticed when navigating on my Edge 830, the Varia alert overlay covers part of the "distance to next turn" marker in the top left over corner of the map. At times I wouldn't tell whether the next turn was 2.2 miles, 1.2 miles, or 0.2 miles away. On one ride I went about 3/4 of a mile with the alert overlay active from cars continuously passing, it took a very long time for it to clear and allow me to see the distance to next turn.
I wonder if the screen could be re-rendered to fit between the alert bars when the alert is active.