Every time you step onto a different train number, you're counted once as a rider. That includes making connections on the same trip in the same direction. On your return journey, you're counted again.
As an example, when I go from ATL to MSP and back, I am counted as six riders -- three in each direction -- since I'm riding three different trains each way.
And nearly every time I've taken a round trip on an airplane, I've been counted as a minimum of four riders -- because it's always at least two hops to anywhere. Usually it's three hops, and I'm counted as six riders. On one memorable occasion, it was four hops and I was counted as eight riders -- and that was just going to a single convention for a weekend and back. An international trip sometimes counted me as 12 or more riders.
Yes, this is comparable. This is pretty much standard for measuring trips, actually.