I'm not sure if it's still the case but most of the population in Mexico is above 3000 feet so recipes had variations for sea level instead (the recipe was made for 1000msnm)
Sometimes it was confusing if you got something imported from the US or some brand that needed to be adjusted for high altitude
But that non zero is extremely close to zero. But it's making more fun about the fact that January 1st is very arbitrary cosmically. Even the solstice would make more sense