Elevation screen scaling

Recently upgraded from an 830. On the 840 elevation screen, I can adjust the scale for height and distance, like I could on the 830. However, it doesn't remember my choices. For example, I wanted the distance to be 1 mile, but by default it shows the whole ride length, which isn't much use on the move.

Is there an "ok" option after saving my setting that I am missing? I can only see the + - and a return arrow. 

NB, I does stick to my setting until I change screen. Once I return, it defaults back.

Thanks.