High/Low when is it collectable?

News: Registration is free here at the CPMF!

I'm just getting into note collecting and was wondering, when does a note constitute a high/low? Or in other words whats worth keeping?
For example right now in my wallet I have a $20 EYW 9266659 would this be considered a high worth keeping?

thanks ZB

EYW 2005 Low 0,000,753  Belleville, ON 
EYW 2005 High 9,720,804  London, ON 
These are current posted high and lows
If you check the WIKI HIGHS/LOWS list (see tab on top of forum for access) it gives you highs and lows for prefixes of various denominations.
Being a newbie as well I did not know this existed until fairly recently.
Hope this helps

FRIEDSQUID