In 1234567, 4 is the median. When there are n odd numbers, the number (n+ 1)/2 is taken after sorting from the largest to the smallest, where 1234567 has 7 numbers, and the number 4 is taken after sorting.

In 12345678, 4.5 is the median. When there is an even number m, after sorting, take the average of the number n/2 and the number (n/2+ 1), where 12345678 has 8 numbers. After sorting, take the number 4 and the number 5, that is, 4.5 as the average.