My advice, fwiw, is to rely as little as possible, at first anyway, on the "numbers in boxes" that your scope spits out and try to learn how to interpret the actual waveform trace on the screen, using the graticule markers and timebase settings and the waveshape. That is, force yourself to use the scope as if it were an _analog_ scope until you have the basics of waveform interpretation down pat. One should always view the DSO's "numbers in boxes" measurements with a grain of salt and try to confirm them as much as possible by the actual visual interpretation of the waveforms.
Also, many DSOs will only use the portion of the waveform that is actually displayed on the screen when giving you the "measurements". So, for some signals, if you are looking at the waveform in some horizontal timescales, you may see very different "numbers in boxes" than if you use other scales on the same signal.