How confident are we in the chronology of the transition between Howieson's Poort and Still Bay?

How confident are we in the chronology of the transition between Howieson's Poort and Still Bay?

Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Human Evolution - Volume 64, Issue 4, April 2013, Pages 314-317

Guillaume Guérin, Andrew S. Murray, Mayank Jain, Kristina J. Thomsen, Norbert Mercier,