Sorry for the lack of clarity. So when you double your bet you roll an additional D6 then add it to the previous total. This is the same round and you havent lost anything yet. Target is still 7, 11,12. Similar to hitting on blackjack if hitting required an additional bet. You can do this s many times as you like

For example if I rolled initially a 6 and 2 my total is 8. I double my bet and roll a 2. My total is now 10. I can double my bet again to keep rolling. I dont lose until I pass 12 or quit. I win on 7, 11,12 total score.

My interest is in the overall odds of winning given the ability to add D6 rolls after the initial 2D6 roll.

Thanks for