I am wondering about the declaration form CBP 6059B. The instructions say: 15. If you are a U.S. resident, print the total value of all goods (including commercial merchandise) you or any family members traveling with you have purchased or acquired abroad (including gifts for someone else, but not items mailed to the United States) and are bringing into the United States.
Note: U.S. residents are normally entitled to a duty-free exemption of $800 on items accompanying them.

Am I supposed to list the $300 worth of clothes I bought in Germany and the $50 worth of trinkets I bought in London? Or only list anything when I have purchases over $800 US?

I've never really understood what I was supposed to list here but now that I am starting to travel much more internationally for my new position I figure I should find out.

Thanks