For both graphs, you are only generating 0.1 seconds worth of data. 100 samples at a rate of 1 kHz. So the graphs are showing exactly what you are giving them.
Now you have it in a while loop, which means you are just doing the same thing over and over again.
Are you getting your waveform graphs confused with waveform charts?
A waveform chart maintains a history of the data that was sent to it and will place later iterations of data in the while loop after the earlier ones.
Two other things.
1. Your Stop button should have the mechanical action of Latch when Released rather than Switch when Released which will cause it to reset and pop back up once it has been read.
2. Set your Simulate Signal Express VI's to simulate acquisition timing rather than run fast as possible.