Manual focus modes

[Rivendell]

When I’m in manual focus mode for video, there is either a green square on the app display (by the EV reading) or, if I tap it, a circle with a dot in it. With the green square, a white square appears in the frame, which I can tap to move around. With the circle, the white square disappears and if you tap the frame anywhere the message “M.Exposure Mode Metering Disabled" appears. If you move the focus ‘wheel’ in the app, you can adjust the focus in either mode. I don’t really know what’s going on here ... any help gratefully received!