[Gordon Steadman]

It is a 'belt and braces' thing. They stay in the trash can for a while, in case you deleted one in error, and disappear over time. While they are there they still count towards the total. Google Mail works in a similar fashion. If you prune your messages regularly then you won't notice this is happening but, if you wait till your mailbox is full before deletion then they clog things up and it needs to be emptied manually.

What's this 'error' word?