What is a level 4c in grades?

There's no universally standardized "Level 4c" in grading. Grading systems vary significantly between countries, states, school districts, and even individual schools. A "Level 4c" might exist within a specific school's or district's internal grading rubric, but without knowing the context (the school or district's grading system), it's impossible to say what it means. It could represent a specific achievement level, a grade letter equivalent, or something else entirely.