Cerbo gx fuel level calculation

Hi All

I have recently replaced a vdo fuel gauge w my cerbo gx. I am using a european sensor with no curve on a 200l tank feeding a volvo penta d2-54 (~2lph). My fuel level has been steady at 150l this last month while at rest. After two hours of running today i looked to see the level reporting below 50%! Digging into the set up i see sensor resistances between 90 and 130. Typically 110osh. W a 10s average i expect this to report atleast 60%. Can you help me understand the difference here?

6hours out from Corfu,

Thanks

Alex