I still want to ask What is the different between X increment and Delta X(The attribute of graph).

[?]

Who can tell me what is the different between X increment and the
Delta X attributes of the graph?

[Cyril]

Rosa,

The X increment is simply the spacing between each major gridlines (you actually have major and minor X increment)covering the full scale range.
For the Delta X it is easier to think of it as a measure of time elapsed between each data point. Let's say you acquire 100 points but each point is taken every dt=4s. If you set your Delta X to 4, the X axis is now going to be 400 (since every point is taken every 4s) while you can still set the X increment to be 50 to have major gridlines every 50s on the X axis.
Hope it is clear enough.

Cyril