Think of a rocker arm as a teeter-totter on your playground. If the length of the board is the same on each side of the pivot, the ratio is 1:1.

Now you are the pushrod at one end and your friend is the valve at the other end. You move up 1 foot, your friend valve moves down one foot if the ratio is 1:1.

Now, you shorten the board so that when you move up one foot, your friend valve moves down 1 1/2 feet.....the ratio is 1.5 to 1.

Dont ask about your friend valve being overweight.