Dangit! I completely forgot - I walked much of that anyway, if the watch had reminded me there was a challenge, I would have done it (only noticed it here on MR some time back). I know, not Apple's fault. But I've done all their other challenges, would have been nice to have the full matching set.
I got my badge and then some! Ended up walking a total of 16.3 miles that day. I'm a tall,skinny guy who hates running but I love all other forms of cardio exercise. I don't necessarily need a reminder to walk but I do enjoy getting the activity rings for the day. Especially when it's going against co workers