Oh, one more thing: make sure you give each Discount a unique Discount Name, as that's what we use to keep track of which discount is which -- e.g., you could have Names like "Widget qty 3-5", "Widget qty 6-10" etc.
Once you Submit the first discount in your series, the settings you'd just saved will remain visible, so you can simply modify those settings (e.g. change the Name and Min. Qty.) and then hit Submit to save the next discount, lather rinse repeat. :^)