I don't know. Maybe Sally Edwards has a typo in her article. Read her books, go to her website, email her. All I care about is the concept which seems to be a universal agreement among trainers. Read Joel Friel. He says the same thing but didn't put the numbers to it which you asked for.

The whole point is that you can burn just as much fat at higher intensity efforts. There was a whole era when we were taught not to get above a certain level because it took you out of the fat burning zone. A bunch of people think that if you can't hold a conversation while working out that you aren't burning fat. Not true. This low level only means that the percentage of fat per calories burned is high and that you can sustain the workout for a long time. These same people that won't push above this level of effort are also the ones that never get faster.