missing posts when I click on a category

I’m very new at this, and I appreciate the help.

I have my posts organized by four categories. I have the main page set up to show the most recent 10 posts, and its fine. On the main page, when I put my curser over a category name it says “View all posts filed under [category name]”. But when I click on the category, it doesn’t show me all the posts, only the last 10. The same problem happens when I click on a archived month; instead of all the posts in that month, I only get 10.

How can I set the main page to show 10 posts while having the categories show all?

Thank you very much.