Yes, it means "make it 10" or "make 10". 10을 만들어 might work better in many cases, but 10으로 만들어 is also possible. 으로 is used after a 받침, as in 십(10), and 로 after a syllable with no 받침 or a ㄹ 받침, as in 팔(8)로 and 구(9)로 만들어. (으)로 means 1) to/toward (a location, situation, or person), 2) a means employed for a purpose, 3) an intended aim or target. 1) 대구에 살다가 서울로 올라왔다: After living in Daegu, I moved to Seoul. 2) 진흙으로 사람 형상을 빚다: Shaped the clay into a likeness of a man. 3) 아들을 키워 과학자로 만들었다 (= 과학자를 만들었다): Raised his son to be a scientist.