A detailed explanation on attendance categories can be found here

Zooming

With a mouse pointer, the zooming is performed by dragging out a rectangle in the chart. The user can't pan the zoomed area but has to zoom out then in again on a new area. When zooming, a zoom out button appears at the top right of the chart.

Exporting

You can dynamically export the current data displayed in the chart to PDF, CSV, PNG and other data formats by clicking on the top right expanding button, and choose your desired format.