Also at a certain period of history in Europe specifically you were only considered to be literate if you could read and write in Latin. They didn’t keep records of how many people could read and not write or how many people could read and/or write but only in their local language.
Probably more people throughout history have been literate or semi-literate than we’ve been led to believe. Probably not everyone. Probably not even most people. But also probably more than you were led to believe.
Also a lot of people could read numbers either Roman or Arabic depending on the time period because people were dealing with merchants and they wanted to know they weren’t being cheated.