Here is a service manual. I haven't read the manual in details but just skimmed it. I noticed pages 3-95 Ink absorber, 3-119 Maintenance unit, 3-105 Flushing base and 3-128 Flushing box.
It seems you have to enter a maintenance mode to reset the ink counter and a special Maintenance printer Driver is also needed. I searched for this driver but found nothing.
But it seems there are other ways of resetting the counter, See this, this and this.