It seems to be a misprint. As 1L / 40 = .025L (25 ml) which would be US 3.2 oz to one US gallon. If 40ml is used per 1L then the mix would be 25:1 (1L / 25 = .040L (40 ml)) or at least that is how my calculator figures it.
Of course I don't fool with exact mix ratios when mixing my fuel as I use a multi mix oil that is designed to be use in 16:1 to 50:1 engines so I just mix in one gallon batches per package. Of course I rinse the package back into the fuel container to get all the oil out. But we do still have fuel oils that are require to mixed by exact ratios.
