That works out at 450 miles per litre. Jaguar have revised their rated from 1000 to 750 miles per litre. For a car that will cover 30k in a year, that rate of consumption is a massive PITA

Click on: English - 2.3L, then click on DUCATO or van ICON. Then click - Electrical Eqiupment - Electrical Functions. Click on area of interest and click on wiring diagram. Your problem will be that a connector will appear on several diagrams. Scroll down to the connector that you are interested in, and then click on that. Your AdBlue solution has a shelf-life which can vary depending on the storage conditions and the type of container used to store the solution. AdBlue contains urea which is degradable by sunlight as well as high temperatures. In optimal storage conditions (appropriate container at room temperature) it may retain its qualities for up to 12 months.
A countdown starting at 350 kilometers indicates a system malfunction that needs to be fixed by the dealer. The normal low AdBlue countdown starts at 1,500 miles (or however many kilometers that is). I thought the same thing. 350 kms = 217 miles. 1500 miles =2414kms. I don't think the OP's issue is running out of AdBlue.
Engines play a part too as some may be too old a design and not be worth upgrading to meet the new standard. Rumors circulating around Fiat’s forthcoming Euro VI engines include suggestions that the Ducato will achieve Euro VI without using AdBlue and that the most powerful motor, 3.0-litre, 180bhp, is going to be dropped from the range.

Fiat Ducato Adblue fault, NOX fault and frequent errors P203F, P20E8, P2BAF - SCR/DEF AdBlue Reset on Fiat Ducato vehicles Adblue malfunction - limiting th

NHSP. 331 19 115 276 389 167 389 189 266

how much adblue does a fiat ducato use