Thanks for answering David but i can't see how that answer is correct. If I am following what you say, what i am counting is any thank yous given to others that have made changes to profiles in my watch list (ie my Family Activity Feed). But this fails on two points - that Family Activity Feed does not distinguish between thankyous from me or from others, and two it does not include activity that I've thanked that is not related to profiles in my watchlist.
If I've read your directions wrongly please explain further.