I have an international travel, which has a domestic stop (SFO – IAH, IAH – LIM). I would like to book economy then apply upgrade with plus points, what confuses me is that:
1. United show me separate upgrade option on each segment: 20 for the first (domestic ) flight and 40 for the 2nd (international) flight;
2. However when I select both upgrades, the combined cost is still 40 points.

My question is: if I use plus points for both segments, will the cost be 40 points, or actually it will become 60 points?

Thank you!