GAG 4.10 bug:
When I enable a boot timer (like '5' seconds) and press enter, it doesn't return to the Setup menu. Instead it returns to the Boot menu and the Setup button is no longer there.
Not a bug, just a confusing screen. That screen (which looks 90% like the regular boot screen), is actually the second part of the timer selection and default OS configuration.
After you have set the time, that screen appears, and you press the number of the OS that you want automatically booted after the timer runs out. After you have done that, you will return to the setup screen once more. That "default OS selector" screen doesn't boot anything, just selects the OS to boot as part of specifying the boot configuration.
BTW, if you need to pause the boot screen (can't remember the key you want, and the number of entries is largish), just press the space bar, and the timer countdown will be halted.