Posts Per Page Problem

(please note i posted this before – but when i searched for it, it was gone!)

I am using the Conestoga theme on my webpage. I have recently uploaded my archives dating back to 2000 with the appropriate backdates. I only want 31 days worth of posts on the home page but it gives me posts dating back years. When I change it to 10 days of posts, it gives me posts till 2002. When I change it to 1 day of posts, it gives me posts through April. Can someone tell me what is off and how I should fix it?

I can give you the web address if necessary.
THANK YOU!