Bitfinex's announcement
'We have finished the BTG snapshot & have assigned BTG to users with a BTC balance at the time block 491406 was mined. (10/24; 01:17:35 UTC)'
I though the snapshot would be done at block 491407 ??!! (as mentionned on bitcoingold twitter account). It makes a huge difference !
I don't know. All I can say is that I've got exactly the same amount of BTG on my Bitfinex balance as I had BTC.