The retrieved data will follow the data layout rules of the graphics API in use. See Compute Shaders for cross-platform compatibility information.
Note that this function reads the data back from the GPU, which can be slow. If any GPU work has been submitted that writes to this buffer, Unity waits for the tasks to complete before it retrieves the requested data, guaranteeing this function returns the most up to date results. For this reason, you should use AsyncGPUReadback instead because it performs the request in the background, and allows you to check when the result is available, without blocking the main thread.
Note: Only blittable data types can be copied from the buffer to the array, the array's type must be a blittable type. If you attempt to use non-blittable types, an exception will be raised.
Additional resources: SetData, count, stride.