How much oil in Td5 Transfer box?

Thought Id treat my 99 Td5 90 to a complete fluid change.. Im sure its never been done!

Did the Axles etc ok but following instructions & amounts from Haynes, it told me that the Transfer box takes 2.8 ltrs. However, only about 1.8 ltrs came out & about the same went back in before it dribbled out the fill level. Am I doing something wrong or are haynes saying something wrong?

Thanks Ian