[sublinear]

It's a percentage of a base unit. i.e. the amount of flour used is 100% of the base unit amount.

Sounds like you want the total percentage which is just as easy to find. Given their example, the total is 170%. The proportion of flour to the total is 100%/170% = ~59%.

Think of it as a "separation of concerns". Using a base unit allows you to measure without regard for the other ingredients. Expressing it in percent allows you to scale a recipe without regard for the literal amounts. It's a good system.

Ever write CSS with "rem" units? It's the same idea.