I've always liked the detail that the space shuttle maximum thrust is rated at 104% because after some flights, they learned that the RS-25 could be run harder

I've always liked the detail that the space shuttle maximum thrust is rated at 104% because after some flights, they learned that the RS-25 could be run harder than the specs required, and it was simpler/less chance for error to just set max at 104% of rated thrust, rather than recalculating everything and changing all the documentation.