Your Walkadoo step goals are based on your own individual walking history.
Walkadoo looks at your last nine days of steps and uses an algorithm to choose a goal for you that sits between your highest and lowest step count during that period.
If you have a few higher step count days in your 9-day history you may find your step goals are a bit higher, but if you have a few lower days your step count will also come back down.
If your goal is toward the higher end of your own personal 9-day spectrum the points for reaching your goal are higher, if the goal is lower your points are lower as well.
There is no setting in Walkadoo to adjust your step goals higher or lower, the site simply adjusts to reflect your own activity level -- challenging you to get more active without pushing you to do more than you've shown you can do before.