Michelle,
That is almost certainly a lippert axle. They come with a sticker on then showing which axle it is, but this many years later, the sticker may have come off.
I would guess that axle is rated at 2800 pounds gross, although it may be 3000 or possibly ( but not likely ) a 3500.
The numbers you are seeing on that sheet you posted above, as others have said, is approx how many pounds are on the axle when the trailer is manufactured. Everything you add to the inside of the trailer adds to the weight on the axle and the tongue.
Honestly, to get all the numbers that tell the whole story, the easiest way is to make three seperate passes over a three platform scale, like a CAT scale. The actual weight on your axle is different when you apply tension to your weight distributing hitch. The only way to really know is to weigh the truck and trailer in two passes, once with no WD applied, and againe with the weight bars tensioned.
Edit, one of the weak links in this chain of parts is the two 14" tires. You likely have load range C tires, and the weight limit of the pair of them is approx 3500 pounds when they are new.