I actually did this post to see how the photos suffered with a lower quality (smaller file-size). Why did I start with 80%? That is the default setting for resize on my compooter. Next I went to 90%, but why not 100%? The 100% quality in .jpg was too large to post.
I didn't bother going below 25%, since the file-size was tiny and to tell the truth the photo still looked good enough to suit me. The differences in detail and color are small enough that for practical purposes, they can be ignored.
Go back to ignoring. Best wishes. G