KeyDown function

I understand the ‘KeyDown’ command behaves "Press and hold the particular key until it release by a ‘KeyUp’ command.

For Example, I need to apply above command for [Backspace] so here’s my script.
KeyDown backspace
KeyUp backspace.

so when I run this, I see a single press action on [Backspace] button and then release (means If I’ve text “ABCDEF” and when I apply above script, only deletes last character ‘F’ but not whole text).

I would expect ‘keydown backspace’ line actually press and hold [Backspace] button, wait for 10 secs and they release [Backspace] button.

Am I correct?
Please correct me If I’m doing anything wrong.

I’ve also followed ‘EggPlant reference Manual’ but can’t pick the odd one out from the above script.

The keyDown command is really only useful with modifier keys. When you hold the backspace key down on a physical keyboard to delete a word or string, it’s the hardware in the keyboard that repeatedly sends backspace commands into the system – it’s an action that’s repeated over and over. Modifier keys work differently. They are setting a state within the system, so you can hold them down and maintain that state – there is no action associated with them.

If you want to issue a bunch of backspace commands, you can say:

repeat 10 
    typetext backspace
end repeat