This is a total of your best runs for each map. There are four maps per world (12 total maps across 3 worlds), and perfect runs usually yield around 10,000. Use the video guides posted in the solutions or on youtube for strategies to get perfect runs.
Once you have totaled 100,000, this will unlock. You can check your progress in the Leaderboard on the Main Screen and update your total to see your current total right away by choosing to "Register Scores" with the X button. You can only do this ever so often, so only use it if you think you are close to your goal.
New Legend PL also says that this is total score accumulated in the game, so you could play the same map and complete it over and over until you reach 100,000 points if you want.