I still don't get it.. I played few hundred satoshis in multiply btc, but still the same % till next free bonus... Bought few tickets in lottery too 
I am not sure how it's calculated (whether Lost or Wagered)
But here is my stats, I have the full 19x bonus:
MULTIPLY BTC WINNINGS
-0.01353939 BTC
I put in 0.007 BTC, activated the 2x Bonus, lost it all ;-)
A few hundred Satoshi might not be enough to move the needle of the bonus progression. Sorry I don't have an official answer. Just giving my anecdotal data.