Should that not be 346% faster? If A takes 1 second and B takes two seconds, then B is 100% faster than A. So the calculation would be (B/A - 1) * 100. Applying this here gives around 346%.
EDIT: B would, of course, take 100% longer than A, rather than be 100% faster.
EDIT: B would, of course, take 100% longer than A, rather than be 100% faster.