Surely the answer is quiet simple, yet I would be interested reading your explanation(s) of this account.
1 Corinthians 15
4) And that he was buried, and that he rose again the third day according to the scriptures:
5) And that he was seen of Cephas, then of the
twelve: (KJV)
The Douay-Rheims bible reads:
http://www.newadvent.org/bible/1co015.htm
5 And that he was seen by Cephas, and after that by the
eleven.
We read verse four gives account of the burial and resurrection, while verse five states Jesus was seen of Peter, then of the twelve apostles.
The interesting fact is Judas Iscariot had betrayed Jesus and committed suicide before the ascension, and Matthias was chosen as Judas successor after the Lord's ascension.
Your explanation(s) ?
Let us leave commentaries out of this discussion, thanks.