There are no stupid questions....only stupid people.
JUST KIDDING! Wasn't that line in a Nat'l Lampoon Family Vacation movie?
Anyway, just thought I'd make an attempt at some levity there. Yea, I know....pretty lame.
By the way, as I understand it (and have read above), the lower the number on the arrow (at least on Eastons, Bemans, etc.) the "stiffer" and/or "heavier" the arrow.
I used to shoot 400's w/my Matthews FX. Then I went to 300's w/my Switchback (mostly because I was hunting boars).
Now me and my Tribute shoot Easton ST 340's. Seem to be a nice balance between speed and punch!
Good luck!