The following quote is found Chapter 17, section 5.3 in the pgf manual. ("This option" refers to the specification of the location of a node by two measurements.):

> 
> The effect of this option is the following. First, the point `(<number or dimension 2>, <number or dimension 1>)` is computed using the normal rules for evaluating such a coordinate, yielding some position. Then, the node is shifted by the vertical component of this point. The anchor is set to south.
> 
> 
> 

I am providing the example provided in the manual. Does the example illustrate "this option"? How does `and 3mm` change the position of the node?

```
\documentclass{amsart}
\usepackage{tikz}
\usetikzlibrary{calc,angles,shapes,positioning}

\begin{document}

\begin{tikzpicture}
\draw [help lines] (0,0) grid (2,2);
\node at (1,1) [above=0.2 and 3mm, draw] {over};
\end{tikzpicture}

\end{document}

```

Does anyone want to offer a better illustrative example?