Maybe nothing, maybe case hardening "lifting" off gears or gears chipping, either keep riding and check magnet for more slivers, or wait for failure or strip and assess. Your call really, I would ride and monitor it myself.
I've had thin round (like straight wire) on my magnet (1199S). I've done a couple of changes and both were similar (maybe less on the second oil swap). I've also taken the sump off and cleared the 'sludge' filter, nothing in there. If everything runs fine I wouldn't be concerned at all. Remember the majority of these bikes are serviced by dealers, to them it would be water off a duck's back:Happy:
It's a fresh rebuild bought off a forum member here. Luigi said it was a 'bit tight' when he inspected it and also said the gearbox hadn't been done and needed it. He found a similar amount of slivers when he did a change... Will monitor...