WHY does PA put a #2 on my truck?

im trying to figure out what the #2 sticker mean?

 

It's the weight class the truck is registered under.

 

If your talking the inspection stickers, because I wondered this myself...If your in a big city one is for mechanical and the other is for emissions. In reading you need two.

 

The post above noting the weight class is 100% correct.

Keep in mind the higher the weight class, the higher your registration cost is.
You can always register lower if you don't tow or carry a lot of weight, since you are at a weight class 2, I would not go any lower.

When I bought my truck i registered it at weight class 2 but could have registered it at weight class 3 per the weight listed from the manufacturer (7200)
In fact the dealer wanted to register it at weight class 3 but since I don't tow more than 5000 lbs, I had them make it class 2 to save some cash every year.
Make sure the title reflects the correct weight (NOT what the truck is registered for). These numbers may be different. For example, My truck is registered at weight class 2 which is 5001-7000 lbs but is titled at 7200 lbs which is from the manufacture. This would allow me to increase to weight class 3 is needed, but I don't see that happening. My dealer I used had no idea about this and I had to walk them through it and they still made mistakes which took weeks/months to straighten out.

Remember even if it was registered at weight class 3 (which is up to 9000 lbs), you should not exceed the manufactures weigh limit, which in my case is 7200 lbs.
increasing my weight limit 200lbs was not work the added expense every year in my case.