Fines on renewed items

It explicitly states on the website that library due notices will be sent out with a seven day grace period so why on the first email I got notifying me that my books were late am I being charged? 


The website says

Whilst items are overdue they may be renewed, even though fines may be owing. 
https://lrweb.beds.ac.uk/libraryservices/availableservices/renewals

If you renew an overdue item the fine is added to your account