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.
usersteve83, 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.