Why does it seem like some lessons are missing from Oodi?

Every now and then someone wonders why it seems like a course is a couple of lessons short of what is supposed to be. A common reason for this misconception might be an inability to read the way a date range is represented in WebOodi. Here’s an example:

date range

When you read this, there are a lot more lectures than four. Date range 27.09.-11.10.16 includes 27.9, 4.10 and 11.10, while 03.10-17.10.16 also has 3 occurrences.

This is the way WebOodi represents recurring events when they repeat weekly at the same time in the same place.