I search the web for explanation for some time. Eventually I stumble into this on a third party ink website.
The easiest method to install Piezography inks on the R3000 is by installing them into the printer as it's first set of inks. The reason for this is that when the R3000 is first turned on and ink cartridges are installed for the first time, the printer performs an ink initialization which pulls in about 15ml of ink from each cartridge into the ink dampers, the ink lines, and the print head. This is not much different than that of the Epson Pro 3880 - and this printer shares many of the same components.Quite a shock.. but OK.. that explains it, so I can move on and sleep peacefully :)