The time taken to complete a Series varies from one to the next.
You can get a good idea of how long a Series will take to complete on its overview page (accessible by clicking on the Series' name on the main Series page):
The number of days tells you how many days you will spend learning, but depending on the Series it may take you longer to complete. This is because many of our Series encourage you to take time out between days to put what you've learnt into practice.
If you have any more feedback around this, find out how to get in touch with us here.