I uploaded a large gedcom (big mistake) and had numerous automatically determined matches which I dutifully reviewed. When the parents of a match were the same as those in my profile I did as instructed and selected the "Ancestor" and "Descendant" option. That made a whole lot of skips on profiles that had not been automatically identified. This is done to prevent a lot of duplicates.
The problem with that was that since I accepted all those skips without further thought, it deleted numerous profiles from my file even though there were no matches.It also created numerous disconnects in the family lines. I am now busily finding and restoring these.
What I learned from this is:
1.Upload in small bites. (as they suggested)
2. Do a manual search on each of the skips that the "Ancestor" and "Descendants" options created before accepting the skip.