You do 3 comparison for each number count
1) compare to current maximum count
2) compare or calculate to the second maximum
3) compare to the number left

Then you get the maximum out by comparison of the counting result.
1) The worst case is n-1 comparisons, if all numbers are different.
2) The best case is no comparison, if all numbers are the same.
3) The most possible case is m comparisons, m << n-1.