You can configure the data rate at which C Series modules acquire and returns data at edit time using the C Series Module Properties dialog box. You can programmatically change the data rate at run time using the FPGA I/O Property Node. The execution of an I/O Property Node that is configured with a Data Rate property overwrites the value you configured in the C Series Module Properties dialog box.
Refer to the datasheet for the module for more information about understanding data rates. The latest versions of the datasheets are online at ni.com/manuals.