Lets start from the top. What kind of vehicle, how many total miles on the vehicle, what are the driving conditions of the vehicle (i.e., highway, farm roads, stop and go, etc.) I believe you stated the oil is John Deere 15W-40 and that it had 4,000 miles on it at the time you changed it. How many months did it take you to go those 4,000 miles?
Now, start at the top of the UOA over in the left had column and list what they say going down. Kind of like this:
Iron - 29
Copper - 10
Tin - 0
Do this from top to bottom so we can read everything. Then we can try and give you the answers you are looking for.