The output message from this Ott didn't include the histogram. I've just followed the steps in this link (ISFS/SensorInformation/OTTParsivel#2.USAGE) to set the message. Since the serial number is reported as XXXXXXX, I'm assuming that it is serial number 410948 (haven't found the record of serial numbers in our wiki(?)) and followed the steps also described by the link to cheat. It now seems to be working as desired.
P.S. Found Tony's serial numbers in AssetPanda, showing that this sensor was 450620, so I've just changed this. No change of the actual sensor.