A sentinel loop looks like the best choice. End the loop when the user enters a negative raw score, since negative values will not occur in valid data.
Other styles of loop might be appropriate depending on circumstances. If the number of raw scores was easily available, a counting loop might be best.
But let us use a sentinel loop. What should go in the boxes of the flowchart?
It is often useful to write out a summary of the data just processed. For now, just write out the count.
Decide what should replace the generic label in each box.