A subset of the data row is displayed as text.
Three things happen when you drag a row onto a shape. One is obvious, and the other two are more subtle.
The first — and obvious — thing that happens: A subset of data from the row appears on the shape as text. The whole row of data doesn't appear, because that would be overwhelming. So Visio chooses two values to be shown. You can most definitely change those to show more, less, or different data from the row. We'll show you how in the practice session coming up and then look at the process more closely in "Link data to diagrams II."
The text that appears on the shape isn't ordinary text — that is, you can't select it and type over it. It's the data being displayed as text.