ACR MLG DEPARTS ARPT WITH LESS THAN DISPATCH REQUIRED FUEL.

Narrative

AFTER DEPARTING PVD ON FLT XYZ ON MAR/FRI/92 WE WERE ADVISED BY OUR DISPATCH THAT OUR RELEASE HAD BEEN AMENDED 45 MINS PRIOR TO DEP AND THAT OUR ALTERNATE WAS CHANGED FROM LAN TO PIT AND MIN FUEL INCREASED BY 1000 POUNDS. WE WERE NOT INFORMED OF THIS NEW RELEASE BY PVD GND PERSONNEL AND HAD NO KNOWLEDGE OF ITS EXISTENCE. FOB WAS 18.6 AND FUEL MINS WERE 18.2 TO FOB. I ENTERED 18.6 INTO ACARS AND WE PROCEEDED WITH THE FLT. WHEN THE WT TAB CAME UP VIA ACARS I COMPARED THE FIGURES AND ALL APPEARED IN ORDER. HOWEVER; AFTER CHKING IT LATER; AFTER THE DISPATCHER CALL; THE DEP FUEL READ 18.8 RATHER THAN 18.2 AS IT SHOULD HAVE; NOT TAKING INTO ACCOUNT 400 POUNDS OFF FOR TAXI. THIS DISCREPANCY WAS THE ONLY INDICATION THAT A CHANGED RELEASE; INCREASING THE FUEL; WAS IN EXISTENCE. AN OVERSIGHT ON OUR PART WITH SIMILAR NUMBERS ON A COMPUTER SCREEN; BUT THE BALL DROPPED EARLIER BY DISPATCH; HE SHOULD HAVE TALKED TO THE CAPT PERSONALLY. PVD OPS AND AN ACARS SYS THAT DOESN'T USE THE CREW'S FUEL INPUT TO CHANGE THE WT TAB NOR HIGHLIGHT CHANGES.