The yellow line is where the bar really first appears.
Tricks of motion
Fröhlich effect
Does the moving bar first appear right above the gray dot?
Yes, right above it, though most people see it appear a little farther along.
Why? By the time your brain notices the bar, it has moved on, and your brain places it where it thinks it is now.
Picture: Drawn by Science Playground · Wikipedia(opens in a new tab)