Oscilloscope Run/Stop output signal
It is not multiple waves at the same time, but rather multiple waves captured at different times overlapping on the display.

These appear on the screen for two reasons:


First, your waveform has zero crossings at multiple places in its cycle, and your trigger is set near zero, so it can be satisfied at multiple points in time, meaning the re-triggerings won't cause the waveform to approximately align as they would with a better chosen trigger condition (say near an absolute maximum).
Next, your scope is operating in a fancy persistence mode where it simulates the delay phosphor of an analog CRT by slowly fading old traces, or even holds them permanently in a uniquely digital manner.  As Steve G. points out in a comment, changing this mode may cause the scope to only display a single copy of the waveform at a time.


And of course if you use the scope in some other mode, such as a single shot capture without re-triggering, you would only see one copy of the waveform.