Bug with max-visible?

While I like the man page, its description of groups/criteria is not easy to understand. For example, it says
"...the config file may contain zero or more sections, each containing any combination of the BINDING OPTIONS and STYLE OPTIONS. "
However, even the following 2-line config gives me an error:
```
[category=brightness]
max-visible=1
```
This is either a bug, or It would be great if there were more examples of allowed configurations in the wiki. For example, how to define a group where notifications overwrite each other (like in brightness/audio level notifications).