I'm no expert by any means but I make it what PP is saying.

He had a $20 Each Way bet made up of the following:
$10 win bet = Loss
$10 place bet @ $4.90 = Win $49 ($39 of their money and $10 of your bonus money).

So $49 less the losing $10 win bet = $39.

I suppose the fine print says they take their $20 bonus bet back if you win anything bringing it down from $49 to $29.

Anyway, frees free.

__________________
Never give up on a dream just because of the time it will take to accomplish it. The time will pass anyway.”

― Earl Nightingale