Any question answered...

Then prob ignore it, and monitor long-term trend (month to month). Obviously, the lower your BF%, the more the reading varies due to other factors - like water composition. You may be losing a bit of upper body perhaps-ensure you do some light trunk chest and arms work, not least to preserve core stab. Then see how it goes.

Cheers bigtwin.. Should really check the water comp as well but typically obsessed with weight and fat.. I do daily 20/30 mins core work for stability and some light upper body stuff (find it helps out of the saddle climbing speed).