First of all, that poster is one of the creepiest things I've ever seen. When I read 1984, I took it as a warning of how bad things could get; apparently somebody thought it was a how-to guide.
Second, I don't care how strict English gun laws are, 59 gun-related homicides is impossibly low.
I'm guessing that they included every single homicide that could possibly be considered "gun related" for the U.S. number; while being infinitely pickier when counting for the U.K. number.
10,000 doesn't sound that high, especially if they include suicides, gang warfare, police shootings, etc. I don't believe the 59 number for a second.