This is an hour after start-up:

The flat part at the beginning is when the normalized value was zero. The RAW value is about 210 higher than this.
The reservoir is a 150ml Aqualis XT and it's currently connected by both 4-pin Aquabus and USB. It's configured as a "Level sensor DELTA 40". Is this correct? Is it faulty or have I missed something?
Many thanks,
Gareth