I was told 150ml.
As this seems very little, and very different to the manual's stated 500ml (????), I measured the oil that I drained first time after buying the bike (06 Boy second hand) and 140ml came out.
On this basis so far I am carefully going with 150ml but am still a little concerned / confused by the manual...surely a prompt reprint would have been in order when the manuals were first issued with such a fundamental error, if that's what it is?
(The sight glass is useless so it would help to know!)