Let me add my interpretation of this graph.
> The Box Speed rating, as seen in the datasheet, is not made with ISO standard conditions, while this film can be used at some higher than 160 speed, if using a "regular" development then our start point should be that ISO 160 found by this calibration.
> This film, with this close to "ISO standard" processing, shows a nice shoulder by +4 overexposure, this is not good or bad, but we should understand how it works. We may take advantage from that soulder to obtain nicely printable highlights, or we may get a pitfall if plainly overexposing to record well the shadows and not underdeveloping N- later. We should understand pros-cons of linear vs shouldered films...
> That shoulder will be different depending on processing, with some N- processing we would have a more linear latitude, with perhaps 1/3 stop speed loss.