Usually you can bet the bonus bet right way. But you’ll have to bet through your deposit in order to be able to withdraw your balance. So I’d say just bet through your initial deposit as a qualifier at the minimum odds, then bet the bonus bet at higher odds SNR.
5-8% is perfect!
Also, if you ever have any doubts about the terms of an offer, don’t be scared to get on live chat and ask. I do it all the time.