semi identical twins? please explain

This doesn’t make sense to me. How can a trlpoid cell have all those chromosomes line up at metaphase and have the right combination of chromosomes be pulled to the right end of the cells? It assumes the cell “knows” that two of one chromosome go one way and the other the opposite way.
In mitosis, the chromsomes are spilt at the centromere and the number of chromosomes stays intact.