Hello,
When you set the timeout in GRUB to e.g. 5 seconds, it will normally
boot first OS on the list, or stop counting when you press something on
keyboard and allow you to make a choice.
But when you press something on the keyboard when the "The highlighted
entry will..." already disapeared (e.g. from gentoo to windows) It wont
stop, but Windows (If its highlighted in the keyboard)
Don't know if it's a bug, but its weird that it still allows you to
change your selection even if its "already booting"