DataGrid surfaces display too many elements with rows and columns set

Question

In my example, the number of rows for Primefaces dataGridwas set to 5, and the columns were set to 2. The table shows 6 items.

This basically went unnoticed until we realized that the button on the 6th element does not work - most likely because it was not associated with the event?

As a minimal example, with XHTML (not showing elements h:head, etc.):

<h:body>
    <h:form>
       <p:dataGrid value="#{testBean.theStrings}" var="theString" rows="5" columns="2">
           <p:commandButton action="#{testBean.printOut(theString)}" value="#{theString}"/>
       </p:dataGrid>
    </h:form>
</h:body>

And bean support

@ManagedBean
@SessionScoped
public class TestBean implements Serializable
{
  private List<String> theStrings;

  @PostConstruct
  public void setup() {
    System.out.println("Setting up array");
    theStrings = new ArrayList<>();
    for (int i = 0; i < 6; i++) {
      theStrings.add(String.valueOf(i));
    }
  }

  public List<String> getTheStrings()
  {
    return theStrings;
  }

  public void printOut(String theString) {
    System.out.println(theString);
  }
}

This will display 6 buttons labeled 0-5, but only a button labeled 5 will not bring the system out of the system.

What's going on here? Should rows not limit the number of elements to 5? Increasing the number of lines to 6 does not change the visual output, but the final button starts working.