The rocket capacity is 5, which works as intended. 5 of out a stack size of 20 is 25 % or 0.25 - but the tooltip says "0.3 stacks". That is surprising to see, as it implies to me that these ratios were hardcoded. That can't possibly be the case though, right?
I know, a critical bug... just wanted to contribute.
Side note: i never realised until today, but I'm 99 % certain that this was an issue since the release version of Space Age.