Sorry, you have already answered my question in your review but I had to read it more carefully:
"Regarding brightness uniformity the SW320’s exceptional uniformity is achieved through a delicate process involving the utilization of high precision apparatus to meticulously fine-tune hundreds of sub-regions on the entire screen. The results of this fine tuning is a noticeable and significant improvement in uniformity over the SW270, and outside of the extreme corners, it measures almost as good as the Eizo CG-318. This is remarkable performance, regardless of price and BenQ is to be commended for their efforts in obtaining this exceptional level of uniformity. You can check how your individual BenQ SW320 monitor performed in its uniformity test on the supplied Factory Calibration Report. "