In the Custom Combinations section of the Hotkeys page, it says, "If the prefix key is also used as a suffix in another hotkey, by default that hotkey is fired upon release"
But I haven't found this to be the case:
1 & 2:: return
^1:: ToolTip("^1 fires on press, not release")
Maybe the docs were instead trying to say that if the prefix key is used by itself in another hotkey, it fires on release?
1 & 2:: return
1:: ToolTip("1 fires on release")
That section also says, "If there is both a key-down hotkey and a key-up hotkey, both hotkeys are fired at once". I think it would be clearer if that was changed to, "If there is both a key-down hotkey and a key-up hotkey, both hotkeys are fired on release."
An example:
1 & 2:: return
1 Up:: MsgBox("The 1 Up hotkey is fired on release.")
1:: MsgBox("The 1 hotkey is also fired on release.")