Is there a way to upload multiple discount counts into CiviDiscount?
I upvoted Zachary's answer, but I felt conflicted.  I do NOT recommend importing directly to MySQL, because you end up bypassing validation logic and could create corrupt discounts.  However, their suggestion of the API CSV Import GUI is a good one, and the one I'd recommend.

If you're not sure what the values should be for your various columns, go to Support menu » Developer » API Explorer.  Set your entity to DiscountCode and action to Get and press Execute.  You'll get something much like you're seeing below.  In the "Results" screen you can see the values, which you can copy/paste.  If you already had discount codes, you may need to scroll down to find one that matches the ones you want to enter.  You can click "Add Option" to set Limit to 0 if you can't see the full list.