Mike,
That is an excellent example on how to handle that situation. That is what I would expect in the best interest of the game. Your ruling however, does not really comply with TDA #41, as written. I like what you wrote and I believe that others will agree; Accepted Action will not be as scrutinized if you could find a way to incorporate language that will consider leniency, or better yet, relieving the caller from unclear financial liability, IF the caller makes sufficient effort (to attain the correct amount) . I wish I had knowledge of this side discussion that you mention.