Blues Berry<br>Berry was a struggling musician. He loved all kinds of music but didn't have any inspiration. On Friday his girlfriend of three years broke up with him. He began writing blues tunes about her. Then his music was a hit and people loved to hear him sing the blues.
Berry's girlfriend broke up with him on Friday the 13th.
The statement is indeed neither definitely correct nor definitely incorrect because the text only states that his girlfriend broke up with him on Friday; it does not give a specific date, so can't be proven whether it was Friday the 13th. I think the system found this difficult to detect because the statement is definitely correct up until the "the 13th" part.