I picked that up too. Awkward. I think they mean that 80% of all calories are provided by wheat, maize, rice, and potatoes.

Yeah, but that statement is basically information-free re: potatoes.

"Boiled squid liver is a popular food. Along with wheat, maize, rice, and potatoes, they make up 80% of all calories eaten by people worldwide."

is technically true, but doesn't tell you anything about boiled squid liver consumption.

FWIW, the data I found puts potatoes at 1.7% of world calorie consumption [0], but also puts the sum of maize+wheat+rice+potatoes at closer to 50% than 80%.

[0]: https://www.worldatlas.com/articles/most-important-staple-fo...

I interpreted it as "they're part of the class of foods that, depending on the culture, can make up to 80% of the calories of each meal'.

The point is that potatoes are one of the top 4 food sources worldwide, and they collectively dwarf the percentages of the long tail of other food sources.

Proportions vary significantly continent-to-continent and culture-to-culture, such that it'd be more meaningless to try and put a more precise (but less accurate) number on it.

This is not difficult to parse out of the sentence if you choose to take a charitable rather than a pedantic perspective, which I recommend to you generally.