The negative number means the car should have had it's oil changed that many miles ago. Oil life starts at 100% for new oil & counts down every 10%. At 15% the display will always show, which means it's near time to change the oil.
, your oil may have been changed but the timer not reset. Reset the timer as shown...
1. Turn ignition to the "ON" position. (do not start engine)
2. Press SEL/RESET repeatedly until the oil life indicator is displayed.
3. Press & hold the SEL/RESET for about 10 seconds until it blinks then let go of the button.
4. Press the SEL/RESET again for about 5 seconds or until the oil life indicator resets to 100%.
Wrench = Maintenance Minder: Symbol letter & number...
Symbol A - Relace engine oil.
Symbol B - Replace engine oil & filter, Inspect front & rear brakes, Check parking brake adjustment, Visually inpest the tie rods, suspension components,driveshaft boots, brake hoses & line (including ABS), all fluid levels & their conditions, exhaust system, fuel lines & connections.
Symbol 1 - Rotate tires.
Symbol 2 - Replace air cleaner element (dusty conditions every 15K miles) & replace dust & pollen filter (behind glovebox) every 15K miles if mainly dusty or city driving.
Symbol 3 - Replace transmission fluid.
Symbol 4 - Replace spark plugs.
Symbol 5 - Replace engine coolant.
All above are taken from the 2006 Civic EX owner's manual.