When I translated "saa" as "watch", duo said this was wrong, and should be "wrist watch". So here I translated "saa yangu" as "my wrist watch", and duo says that is wrong and should be "my watch".
I had the same issue and reported it ( 2017-05-26 )
report it should you see either sentence again.
"My clock" should also be accepted.
It is now, 20/06/2018
frustrating! sometimes they want you to say wrist watch and at other times watch when they are the same!