Sorry if I am not making it clear. I will use 2 SWUs (for a round trip).

The LH flight from FRA-VCE is a A320. If I understand correctly and assuming that I want to waste my SWU on short-haul flight, I will need to give LH another SWU for the FRA-VCE segment (above and beyond what I will give UA) in order to get that segment upgraded.