Romans 9
"Christ was not shortchanged at Calvary, but acquired ALL those for whom He paid." Steven Lawson
Limited Atonement and 1 John 2:2 "Jesus is the propitiation/atonement for our sins; and not for ours only, but also for those of the whole world."
The sins of the whole world - can mean either:
A) Every sin ever committed, and thus the sins of every person who ever lived. - However, this could imply that no one is going to hell, since Jesus has atoned for all sins. We know that people are going to hell, based on the warnings of Jesus (Matthew 10:28), verses in Revelation, etc.
OR
B) Every sin of those who put their faith in Jesus, throughout the whole world.