Ah, come to France, maybe that explains my "sure of myself" answer in the parent comment. 0.0*01% + "à-valoir" is very common and cover the situation described here (eg you get paid a paid royalty, in advance, if the revenue ever exceed you are owed it, but if it's always under you never have to pay back).

Sort of a "I pay you 100€ but if this turns out to be a billion euro thing you get you gold ticket too".