My sister got a report from the ancestry.com website after giving them her information, which, of course, applies to me too. In the subheadings for each region appeared the term “low confidence region.” What does this mean?
From here.
Or in other words, DNA matching, particularly in terms of assigning you to ethnic classifications, is a set of statistical artefacts, not a 100% exact science - and whatever the arguments about the classifications, the statistics are only going to be as reliable as the information in the underlying database.
What puzzles me is that while the qualifier appeared after “African,” “Asian,” and “Pacific Islander”–each of which showed only “<1%”–Europe was the only other component, with 97%, and it too was described as a “low-confidence region.” 
You’re not from around here, are you.
Otherwise, I have nothing. ANCESTRY is a black hole.
I think you have a web interface problem, not a DNA testing problem.
I’ve never done the ancestry.com thing, but I don’t think you are reading the report correctly. Look at what’s shown here, where the unsub is also 97% European:
Below European, after the initial breakdown of high percentage European areas, there is indeed a button “(+) Low Confidence Region”. But it is not an attribute of the European region. I think it probably indicates that additional low confidence regions in the breakdown of Europe are hidden, and can be revealed by hitting the button (hence the plus sign).
I see what you mean…but I saw the chart on a page of my sister’s communication on Messenger–a reproduction, so I couldn’t do anything with the line on the chart. I’d have to ask my sister.