At united healthcare $UNH (+0,09 %) went down quite a bit today. However, I got a fright when I looked at my portfolio and saw that it was down 17%. If I click on the value, however, we only see -7%, which looks better again.
How can this be? I recently had something similar with Porsche AG $P911 (-1,01 %) and customer service wanted to take a look at it, but after a few inquiries I didn't hear anything more about it.

PS: the two screenshots were taken a few seconds apart.
