You want answers? You got answers.

Ten:

Jn.20:19-24
"Then the same day at evening, being the first day of the week, when the doors were shut where the disciples were assembled for fear of the Jews, came Jesus and stood in the midst, and saith unto them, Peace be unto you.... But Thomas, one of the twelve, called Didymus, was not with them when Jesus came."

This is correctly identified as having 10 disciples having seen Jesus. Since Judas was dead, and Thomas was not present, there were only 10.

Eleven:

Mt.28:16
"Then the eleven disciples went away into Galilee, into a mountain where Jesus had appointed them. And when they saw him, they worshipped him."

Thomas was present when the angel instructed them to go to Galilee - he went with the disciples to Gililee, but wasn't with them when Jesus came. It's not as if there weren't other places to be in Galilee.

Mk.16:14
"Afterward he appeared unto the eleven as they sat at meat, and upbraided them with their unbelief and hardness of heart, because they believed not them which had seen him after he was risen."

If you look at the surrounding verses, you can see this is a summary of what happened. Jesus did in fact appear to all eleven when they were together - he appeared to ten of them before that, but just because it does not mention that, does not mean it did not happen. The Gospels are different accounts - the authors focus on different parts of Jesus' life and their walk with Jesus.

Lk.24:33, 36
"And they rose up the same hour, and returned to Jerusalem, and found the eleven gathered together...And as they thus spake, Jesus himself stood in the midst of them, and saith unto them, Peace be unto you."

This is a classic case of SAB's habit of taking things out of context. If you read it with context, you get something more like this.

Lk.24:22-25
"Yea, and certain women also of our company made us astonished, which were early at the sepulchre;And when they found not his body, they came, saying, that they had also seen a vision of angels, which said that he was alive. And certain of them which were with us went to the sepulchre, and found it even so as the women had said: but him they saw not. Then he said unto them, O fools, and slow of heart to believe all that the prophets have spoken?"

Here we see a clear account of people (not disciples) investigating Jesus' grave.

Lk.24:24-26
"And they rose up the same hour, and returned to Jerusalem, and found the eleven gathered together, and them that were with them saying, The Lord is risen indeed, and hath appeared to Simon. And they told what things were done in the way, and how he was known of them in breaking of bread. And as they thus spake, Jesus himself stood in the midst of them, and saith unto them, Peace be unto you.

These people went and saw Jesus, who was with the disciples already. Taken out of context, the meaning is wrong.

Twelve:

1 Cor. 15:15
"And that he was seen of Cephas, then of the twelve."

This doesn't even make sense, it's not even saying that the twelve saw him. It's just saying that he was one of the twelve disciples.

338 to go!