no for some reason it is correct and wished for the CF1.9mod that different cargo needs different amount of cargo-space. so the bigger the cargo "would be" as more space does it takes to load on your ship. so no worries, it's no bug neither is your installations screwed upoh and welcome to CF
np.singleplayer is normal story mode from beginning to the new crossfire-campaign and open singleplayer is just plain singleplayer, no story, no campaign - just npc, open space and you (Hidden Content)