What am I missing?

I received an email from eBay today, which states:

 

90 items sent ; 0% sent with (or as ) untracked letters.

81% valid for trackable services.

 

All items I have sent have had sent have had tracking downloaded.

 

All items have been sent through Australia Post.

 

Am I missing something I should know about?

 

Or is eBay's maths worse than mine???

 

Thanks for any help.