It sounds like you could do a mass edit of card quantities from the option in the Collection Summary screen. Reduce down one for each number. That assumes your listing has your quantities clumped and not broken out by individual line (i.e., if you have 5 of #89 it shows 5 next the the card number and not listed 5 separate times.
Once broken out you can then use the Add to For Sale/Trade option to add the those cards in. Or use the drop down option to add in.
When the sky is coming down
When you feel like you're going to drown
When you know the end is all that you've been looking for
When the pain is too much to bear
When there's no one who will care