I would suggest going into your game settings , advanced options and turning on display putting power. Then whenever you play practice games it will help suggest what power you can use. This is not 100% accurate but it will help you learn how to adjust for the green speed and hills.
The distance displayed on the putting meter when it says 30 feet, really means it should go 30 on a flat surface and a green speed of somewhere around 10/normal. So if the green speed it faster the ball will go more than 30 ft.