Hi there! Thank you for taking the time to create this post. In general, quizzes have one grade/score that is synced to the grade book. There are several options on how this grade/score is posted. If you are trying to create a score only the instructor will see you may consider setting the quiz to manually post grades. (This guide has steps on that process). This is helpful if you want to check and see how a quiz might impact students' final grades.
You could also use "fudge points" to add points to give points to a student. This will show the original points earned along with the extra "fudge points" that were added or subtracted from the score. Here is a guide on fudge points.
When you have a moment, can you please share what your end goal is, with two scores? Are these scores for you and for the student? Is one score a draft and the other a final? Once we know more about the end goal, we can formulate some solutions for you.