As I told my DW you will know the grey tank is full when the sink backs up into the bath tub. :) :) And she thought I was kidding.
If the TT is new and you are sure the tank is empty. I would have the dealer check the sensors. You will find that eventually grease and scum can mess them up as well being off level.
Because the tanks are long, wide and thin it does not a lot of slant to get a false reading. However your TT in new and I assume the tank would be empty.
I kind of like things to work right if they are new.
Good Luck