Tap the Lock button to block any inadvertent readings. Hold the Unlock button to re-activate the screen.
The last ten readings are stored, with the most recent five being visible. Delete recent readings to retrieve older ones.

Take a photo of your sextant at the marked time, so you can check easily double-check your reading.
Pinch and zoom on the photo to get a really close look at the scale.
Delete one of the 5 stored readings if you have tapped by mistake.