Dt is delta time or the time between samples. That example is setting the t0 or start time. The only reason it works is that the Wait (ms) is set to one second which is the default dt. Anything else, would have to be wired to the XScale Multiplier property. Look at example called Real Time chart. And, as I mentioned, you can use a waveform data type. It's a cluster that contains t0, dt, and a y array. If you turn on context help (which you should always have on) and move your mouse over the graph on the diagram, the context help window will show you how a regular cluster can be used.
At this point, only you know the sample rate, etc of the data since you did not provide the code. No one but you even knows what hardware you are using. If you wrote it, it should be easy for you to modify the returned data.
