So the longest subway ride in NYC is 24km (15 miles) and 1h long? We have multiple underground lines farther than this in Berlin with the longest being 32km (20 miles). But don't get fooled, the issues are the same.
I did the same on the first ride. It is a game, you have to go jumping on different lines to get your longest.
It's a game. You're supposed to click on the different route options that are presented to you on the bottom of the screen. That's why it goes slower the more options there are.
But I also just followed it for the first time from beginning to end, not doing anything. Because I assumed someone had already done the math.