Steps to reproduce: 1. Attach a file to an email 2. send the email 3. select the file in your sent folder 4. Note the size [file.txt text/plain (255219 bytes)] 5. click the link to view the attachment 6. the text file should be seen now in the message window 7. select any other message to view 8. select this sent message again 9. Note the size [file.txt text/plain (252907 bytes)]
It's the encoded size.
Why does the size show the encoded size sometimes and the un-encoded size other times? If that's a feature it's not well thought out.
Thinking more like you all do, this is a documentation bug. Maybe add this to the docs: "When viewing the attachment size, on some occasions the size will be shown as the encoded size while on other occasions the size of the attachment is shown as the unencoded size. Occasions are defined elsewhere, see smidge, jiffie, shake-of-a-lambs-tail, etc."