Simulink Data Acquisition with NI USB 6259

[zrxxg]

As shown in the picture, I have connected my data acquisition card in Simulink, and I want to provide a sine signal to the external system through the data acquisition card. I have already achieved this. I also want to use laser sensors to collect displacement outputs from external systems.
I set up the collection module as shown in the picture. I want to sample at a frequency of 500 times per second, should I set my sample rate to 500? How should I set my block size? What is the relationship between block size and sample rate? Each block size seems to correspond to a line on the oscilloscope, as shown in the figure. What is the relationship between the many lines I finally read on the oscilloscope and the actual displacement output of the system.
What I mean is, how can we obtain the displacement output data of the system through so many lines?

Thanks a lot for your help！