PISA is a statistical measurement tool designed for sensitivity to differences in student performance. So it uses questions that some students are expected to get right and some are expected to get wrong, and places the result on a bell curve fit to a reference population.

It's not clear what you mean by "sufficient reading literacy," but I guess it's one of the PISA proficiency levels. Those are simply equally-spaced intervals on the bell curve. For example, level 1c in reading is 2.4 to 3.1 standard deviations below the reference mean and 21% of participants in Iraqi Kurdistan and Lebanon scored at that level. Relative to the baseline, they are definitely close to the bottom. However, even they must've gotten some questions right, or they would've ended up in the "below level 1c" bucket (like 3% in Iraqi Kurdistan and 5% in Lebanon did). (https://www.oecd.org/en/publications/pisa-2025-results-volum... Table I.B1.2a.11)

If you wanted to know how many people achieve "sufficient reading literacy," you would need a test specifically designed for measuring it (i.e. not PISA), where people with sufficient ability can be expected to get all questions right. For example, the literacy rate is typically defined via the ability to "read and write a simple statement about everyday life," a test which 99% of adults in wealthy countries pass, 92% in Lebanon and 84% in Iraq: https://ourworldindata.org/grapher/cross-country-literacy-ra...

Of course a test that 99% pass just becomes table stakes and boring, whereas PISA with its large differences between individuals is much more exciting, but you shouldn't let that mislead you into thinking that students scoring relatively low on PISA necessarily must be lacking even those table-stakes skills.