Alde Hot water icon

Hi All, on my 2021 320S BD, is it normal for the ALDE hot water heater icon (the triangular bar next to the shower head icon) to go empty/blank after some time when the water has come to temperature?

To me, when going into the Menu and hitting the “+” on the shower Icon, the triangular bar fills in But when I return to the menu, it goes back to being blanked out.