The Weather's Closing Down, but the Light Says Slow Down, Get Ready to Stop

Exposure compensation was -1. Adjustments were subsequently made with levels, brightness and contrast, etc. The "Exposure Bias Value" below is gibberish to me--as I said, the exposure compensation was -2. --Landrum Kelly

Exposure Date: 2010:05:28 17:30:38;
Make: Canon;
Model: Canon EOS 5D Mark II;
Exposure Time: 1/500.0 seconds s;
FNumber: f/4.0;
ISOSpeedRatings: ISO 800;
ExposureProgram: Other;
ExposureBiasValue: +-20/6
MeteringMode: Other;
Flash: Flash did not fire, compulsory flash mode;
FocalLength: 100.0 mm mm;
Software: Adobe Photoshop CS2 Windows;