Extra note visible when translating from staff to TAB

I'm not following. I see two notes on the standard staff and two notes on the tab staff. Since it is physically impossible to play two notes on the same string, attempting to use Ctrl+Up to move a note onto a string occupied by another note simply moves the other note to another string as well to preserve the essential quality that there are two notes. At no time do I see any fewer than or any more than two notes. Am I missing something?

For example, try clicking the 0, pressing Up to turn it into a 1 (thus raising the pich of course), and *then* moving the 5 to the fourth string. You'll see it moves there - becoming 0 in the process - and the 1 moves down to the fifth string, becoming 6 in the process. At all times there are exactly two notes, but moving one onto the string occupied by the other causes the other to move as well.