If the timebase is 500us/div or faster, then the sampling rate should be 1 GSa/s
If this is not the case then it may be that you have two channels enabled on the scope. Try loading this data file
There are three parts that define how the scope is set up.
- Time on Screen / Timebase
- Number of Samples requested per screen
- Sample Interval / Sample Rate
If you use Views->ViewProperties to show the properties panel on the right, this will show how the scope is actually set up. The timebase is the fixed parameter, the software will then try and capture as close to the requested number of samples as possible, which means the sample rate is the parameter that drops out of the calculation.
If you use the SDK and write your own application you can change this around, and collect an exact number of samples at a given sample interval, provided there is sufficient memory on the device.