Next time, screenshot the whole page (including market fills) so we can see whether the order is getting filled.
Would it be possible that way to work out how big their order actually was (or would that require an api call)?
Roughly. Can't say for sure since there could have been multiple traders with orders at that price.
Dunno if it is fairly legit or not since it could've been placed a few $ away from the price when it was created (with a potential long elsewhere if they were trying to make a profit from it)... Though I'm not sure that would come down as spoofing or not - could've just been a standard usage.
A spoofer generally pulls their order when the spread gets close, and especially if their order gets nibbled on. If it was intended as manipulation, the fact that the order was at the top of the bid spread tells me they are an amateur placing orders manually.
Spoofy was definitely run on an algorithm.
