'99 fuel injection harness puzzle

I have a '99 Century with the 3.1 vin M. I'm in the process of a rebuild and am installing the wiring harness. The fuel injection connectors are numbered 1 thru 6 but appears they do NOT corespond to the cylinder #. In other words, the harness injector labeled "1" does not go to cylinder "1". This seems strange but I was very carefull to lable everything. Is this the way GM did it or did I screw up. Of course, the engine is a SFI so it's important to have the computer turn on each specific injector at the specific time.