In Garmin Connect online, the percentage of step goal achieved maxes out at 100% in both the Steps widget on the dashboard and the Daily Summary page, even though Garmin Connect will recognise if/when you achieve 200%, 300% or 400% of your daily step goal and award badges (the first time you achieve one of those levels) accordingly.
In the Garmin Connect Mobile apps, the percentage of step goal achieved does not max out at 100%.