I might be a little controversial here lol but i have never weighed Tuna although i am a stickler for keeping 100% to plan for other things..i do Green Days and eat quite a lot of Tuna, a can of Drained Tuna is 139g so to leave 19g out that i may not use next day is a waste..and its not done my weight loss any harm i always use the full drained can of Tuna
i also do not weigh my tuna and use the whole tin i weighed it this morning after reading this post and mine was far less than the amount quoted on the tin also x