Interesting question, and I didn't spot the different values in each column either.

So there are two things going on here to confuse us. First is the fact that different values get put in each column because of the i vs i + 1 for the second insert in the loop. Second is the fact that the ordering is different in each case (which is what I thought the question was about). So for ordering by iAsInt we have 1,2,2,3,3,4,4,5,5... and ordering by iAsString we have 1,1,10,10,2,2,3,3,4...

If the same values were put in both columns, we would still get different numbers of rows returned for all values of @x greater than 3 since ordering by iAsString would give 1,10,10,11,2,2,3,3...

A good reminder (if we ever needed one) to put integers in integer columns!