Understanding log messages

Hiya,

First off, thanks for this amazing plugin.

Second, I’ve got a (probably dumb) question. I ran the first round of bulk optimizations with everything tuned to max – optipng optimization level set to level 5, pngout optimization level set to level 0, removing all metadata, etc.

Then I ran another round and here’s what I see – http://imgur.com/a/Y3vRe
So what exactly does ‘Reduced by xxx – Previously Optimized’ mean in this case? Does it mean the image has been previously optimized and no further optimizations were made at this point? Or does it mean the image was optimized again with even more savings during this 2nd run?

Thanks.