His estimate is that since the year 2004, average loss is 900km2/year. That means imagine 900 extremely large ice cubes which each measure one kilometer by one kilometer by one kilometer. Now visualize that you subtract that amount of ice from the arctic sea every summer.
We have around one month to the end of arctic melt season. We are currently on track to break the record for low ice, the one that was sent only five years back in 2007.