Click the green flag and wait a moment, then look at the total time and per-item time (both in seconds) for how long it takes to add an item to the list.
This times how long it takes to add an item to a list. It adds 100,000 items to a list and times how long it takes to do it, then divides the elapsed time by the number of items added to get the time to add each individual item. Written to give this forum answer: https://scratch.mit.edu/discuss/post/7357980/
