The first line in my reply told you. It's a Fisher Body number, which is the "body number". It has nothing to do with the assembly plant process numbers. It does, but once it leaves Fisher it sorta doesn't. Since the body is set up prior to getting an assigned VIN number, the body tag takes its place since the body assembly took place first and the VIN came along shortly thereafter. A chicken or the egg thing. But if you find some broadcast sheets in the car anywhere, they usually have the body number on them as well, as well as the build sheet (different than the broadcast sheets). One problem is that Pontiac plant was a lot like Lansing plant. Very meticulous about sweeping out the cars and rarely you'll find a build sheet in the car.
The Pontiac plant was a bit odd. They'd build the bodies over at Fisher, then truck the completed body assemblies over to the assembly plant. It wasn't a cradle to grave operation.
If you still have the window sticker, there's a number near the bottom that matches the one on the trunk sticker (your number is 068774) and I've found these numbers are normally close to the cowl tag body number, but they never match. I have no idea why they don't match or what those numbers even mean.
By the way, your GAWR REAR on your decal appears to read 2286 LB/1037 KG. The very last number of your GAWR FRONT KG is ...0, and the very last number of your GVWR KG is ...7 KG. It doesn't get to the bottom of it, but at least 1/3 of the numbers on that decal will be correct for your car.