Now of course Christ appeared to Paul after the ascension; all the other appearances of the risen Lord were before his ascension. But after his ascension, miraculously, amazingly, he appears to Saul of Tarsus.
Some people call themselves apostles today. Well one of the qualifications of an apostle in the New Testament is that he had seen the risen Lord, and if Paul was the last to whom the risen Lord appeared, then there can't possibly be any more apostles. ‘Last of all he was seen of me also.’