I agree. However, considering that Kepler is not actually sensitive enough to detect Earth sized planets in the habitable zone of sun-like stars, both these numbers are extrapolations and it must be assumed that the 7-15% or 20% are well within each other's error bounds.
On the abundance of extraterrestrial life after the Kepler mission Amri Wandel
Some recent calculation of the Drake Equation with estimates of the likelihood and logevitiy of civilizations
Related: The Great Filter and Planets in the habitable zone, the Drake Equation, and the Great Filter