The elevation chart is the height of the line you are about to run, drawn against distance. A bump is a climb. A dip is a descent. The compact strip under the metrics is enough to see whether the run is flat. E, or the expand control, opens the taller chart when you want the shape.
Hover the chart, or hover the route on the map, and the tip follows. It shows how far along the line you are, the height at that point, and the grade beside them. Grade comes from the neighboring samples: the change in height divided by the distance between those samples, as a percent. +4.0% is a short climb. −2.0% is a descent. 0.0% is level between those two samples.
Grade is local. A steep sample pair can sit inside a run whose total climb is small, and a gentle pair can sit on a long hill. Read the tip for the spot under your cursor, and the ascent total on the metrics for the whole line.
Avoid hills, on Low stops, asks the router to prefer gentler streets. It does not flatten the chart after the fact. If the tip still shows a climb you do not want, drag a stop or insert a waypoint onto the street you would actually take. The chart redraws from the new line.