HONG KONG: Mark 6 Crazy

Hong Kong Mark Six lottery jackpot is now 100 Million Hong Kong Dollar.Next draw is on Friday 20.05. - means today.
Until closing of Thursday night tickets turn-over was HKD 171 Million.
Lets bet they will at least crack the HKD 250 Million in selling by this evening
before closing the selling at 9.15 pm HK time.
But one thing please somebody explain to me:
They are all saying 1st price is now 1 Billion - actually 1 Billion = 1,000 Millions -
how can this be HKD 100 Million ? 1 Billion is much more than HKD 100 Million.
I know the chinese have problems with too many zero's - I have checked already
Wikipedia & other sources but couldnt find any clear explanation why they call
HKD 100 Million 1 Billion.
Anybody has a clue on this ?