How TP / FP / TN / FN are measured here
Actual positives (+) are blue-outlined targets; actual negatives (−) are gray/tinted targets.
Shooting a target = predicting "positive" for that target.
• TP: hit a + target.
• FP: hit a − target.
• FN: a + target left unhit (predicted negative).
• TN: a − target left unhit (predicted negative).
Accuracy=(TP+TN)/N, Sensitivity=TP/(TP+FN), Specificity=TN/(TN+FP).