[outop]

No, N means 10 in both parts of the sentence you quoted.

> when the average span between arrivals is [10] minutes, the average span experienced by riders is [20] minutes.

>The average wait time is also close to 10 minutes, just as the waiting time paradox predicted.

The average wait time is half the 'average span experienced by riders', since the rider arrives, on average, halfway through the average span.