How do I see what kinds of seeds and how many of each I have on hand?
To get accurate stock reports, you have to assign a bookkeeper on the nobles screen n. With the bookkeeper entry selected, you can press s to bring up the settings for the bookkeeper position. Here you set how much time your bookkeeper will spend updating stock records. The more precise you want the records, the more time the bookkeeper is going to have to spend counting things. Then you'll need to assign a meager office to your bookkeeper. Wait a little while and the stocks screen ( z ) should be more accurate.
You can access the Stocks screen via the Status screen, which you can access using z.
The accuracy depends on your bookkeeper.