I knew something was off: Math Training on the way.
NPD shows this chart and denotes 'thousands' for the numbers. Well, you multiply the numbers, 1850 for GTA4 360 by a thousand, or 3 zeros, then you get 1.85 million. In your graph, GTA 4 total, sold close to 6 million. Your number '600' multiplied by a thousand, or 3 zeros, would mean 600K. You are off by a factor of 10. You should have used either 'in units of 10 thousands' on the y axis or add an extra zero on the numbers on the yaxis..
*brought to you by the United States of North America Education Department for Edutainment and School Shootings and Chicks in Hot skirts.
*forwarded to Europe with the title: 'Suck it Yurop with your funny accents'