How to delete original images

I have used the EWWW image optimizer but thought I’d try yours. I turned it on and had it scan; it found — I thought — about 10 images. Because they were the most recently uploaded images, I went ahead and clicked “Save Originals,” since (1) if there were problems, I could retrieve the originals, or (2) if there were no problems, I could presumably locate the images in the most recent WP uploads folder and delete the originals — that is, if the optimizing worked and I had no need for the originals. After I started the optimizing, suddenly the plugin started finding more and more images, images it had not shown at the beginning. I did not want to save all those originals and bloat my WP content, but there was no abort of stop button that I could see. After more than 1500 images (out of 2500 on the site), my WP content was half again as big. Your optimizing apparently worked, but I don’t need the originals. How can I locate the originals only and delete them after this optimization? Do they now have any identifying feature? I cannot individually search 2500 images and would prefer not to be stuck with the data bloat. Thanks.