If you have a repeating waveform that lasts for 0.28 seconds, and if you wish to see two complete cycles, then the time required to see two cycles is 0.56 seconds.
An oscilloscope generally has a display which is 10 cm wide and that is 10 divisions. So, if you want to see 2 cycles of a waveform, then the horizontal sweep time is 0.56 seconds for 10 divisions or 10 cm. That works out to 0.056 seconds PER DIVISION. The timebase speed setting would then be 56 milliseconds per div. Because 56 ms would not be available but generally 50 milliseconds would be, you set the time per div switch to 50mS/div. You would see nearly two complete cycles so if you changed the time/div switch to 100 mS/div, you would see 3.57 cycles. If you wanted to see an exact number of cycles, you could adjust the 'FINE' knob to get the required number of cycles displayed.
Seeing all of this requires that the horizontal trace is 'synchronised', so that with each successive horizontal sweep, each successive display is positioned exactly on top of the previous display. This need brings up the ugly subject of 'triggering', and, how to achieve it.
Has this answered your question raised in post #19?