While the Recorder window is visible, all the function keys of your keyboard will change to its shortcuts. This means that if you press the F3 key on any screen, the Stop button of the Recorder application will be pressed, and the recording will stop.
However, if you do not need this functionality, you can disable it.

If the first option (Don’t use hotkeys ”F2 … F12” in vUser Recorder) is selected, then the Recorder application will not bind these keys, and you can no longer use them as shortcuts. For example, if this option is selected, and you want to stop the recording process, you need to click on the Stop button yourself.
If the second option (Use hotkeys ”F2 … F12” in vUser Recorder) is selected, then the Recorder application will bind these keys, and you can no longer use them on other apps.

If none of these options are selected, then the function keys will work in both the Recorder applications and all other applications.