You are correct - the screenshots on the example page do show Month and Agenda horizontally, but I think that is just for demo purposes, although I don't know why it look's like that. If you have ai2ec installed, what you see on the calendar itself, are two dropdown buttons at the top of the calendar: first dropdown button is the display format and it is titled with whichever display mode set as the default in the settings, or the mode that was selected last (the options are: posterboard, stream, month, week, day, agenda). The second dropdown button is titled Categories and list the categories you have created. In my case I have four categories.
What you see in Appearance > Calendar Themes in the Dashboard, simply show what two of the display format options (Calendar and Upcoming Events, in this instance) if you select that particular theme). You don't get both at once.
Kinda' confusing, I admit, but it is what it is.