I'm guessing the X means external or something like that, so basically a course not taken in your school board. Universities won't even know. When your transcript gets uploaded to OUAC the last digit gets dropped. That digit is for individual school boards' administrative purposes and is board specific. As an example in my school board the last digit 9 is used for AP courses, 8 is for IB courses, E is for gifted/enhanced, and Z = online e-learning to list a few. The universities don't see any of that. All they will see is ENG 4U.