I have a Japanese Prius Alpha 7 seater with Japanese Radio player NSZN-W64T. In this player, there is a option for setting fuel consumption data but I couldn't set them. At present, it shows only average consumption data which not match my present consumption. Does anyone familiar with this Japanese radio player?
It's hard to see the Japanese characters in the area you circled but if the layout is similar to the English version we have here, that area is actually your "Best" consumption. The one on the right at 16.1km/L is average (you're correct). I guess you need more than one entry to get a "best" number to appear. (Right now, there's only one as indicated by that single bar graph on the right) Here's the American version:
