First to answer and accepted with score of 10 or more
is indeed ambiguous, but the clarifications offered there show that "score" is synonymous with "net upvotes," so the bounty doesn't help. (Nevertheless, although the bounty of +50 is irrelevant, with its reputation-equivalent of 5 upvotes and three net upvotes, you haven't even (yet) earned the equivalent of +10 upvotes reputation for this answer.)
Incidentally, answers with +10 net upvotes on this site are rare: most questions are sufficiently specialized that few readers feel qualified to vote responsibly on the answers. The "Nice answer" badge (awarded for +10 net upvotes) has been awarded for just three percent of all answers. The "Enlightened" badge (of which there is at most one per thread) has been awarded on less than 1.5 percent of the threads.