If the 'expanding balloon' explanation is correct, then thetexan and I have to be on the right track. From what the staff said, this and other diagramable conventions are actually incorrect. On the other hand, neither thetexan nor I invented them -- these were invented and drawn by physicists...
thetexan has a good point. Ten Billion years ago, the universe was considerably smaller than it is now, so something must have been 'outside the borders' of the universe then; five billion years after that the universe, though still considerably smaller than it is now, had expanded into that...