How do you count by 8 but al the 8?

To count by 8s, you start at 0 and repeatedly add 8 to the previous number. This gives you the sequence: 0, 8, 16, 24, 32, and so on. If you want to count all the way to a certain limit, just keep adding 8 until you reach or exceed that limit. For example, counting by 8s up to 40 would yield: 0, 8, 16, 24, 32, and 40.