When I recently booked a one-way ITO-OGG and selected the ITO-HNL-OGG option, I was surprised to see that it credited as only 500 miles (unlike the way, say, United Airlines does segments).

I don't know whether it would have credited as two 500 mile segments if I had instead use the multi-city option to book the segments separately (and the price may have increased that way too).