On Windows, you can set the buffer size and sample rate for your Focusrite audio interface via the Focusrite Device Settings panel. You can find this by searching in the Start menu.

Start → ‘Focusrite Device Settings’

It can also be found through the Focusrite Notifier in the system tray on the taskbar.

If you can't see the Focusrite Notifier on the taskbar, please refer to this article: Why can't I see the Focusrite Notifier icon on the taskbar on Windows?

The sample rate selected here will be the only option that appears in Control Panel → Hardware and Sound → Sound.

Certain DAWs and other software can also control the sample rate and buffer size. If the configuration in Focusrite Device Settings changes from the one you have selected, check for sample rate and buffer size settings in your other software.

If you'd like to know more about what buffer size and sample rate are, see this article: Sample Rate, Bit Depth, and Buffer Size Explained.