The article is pointing out that:
1. Most ocean plastic enters the ocean from East Asia (80%)
2. Only about 5% of its enters the ocean from North America or Europe
3. But some plastic waste is exported form North America or Europe to Asia.
4. So is it plausible that the true waste share of NA and Europe is higher?
5. It concludes, yes, North America and Europe contribute as much as 5% of ocean plastic directly and then up to a further 5% via waste export.
It doesn't contradict itself, your parent poster didn't "just pick a random sentence from the article," and you should maybe read more carefully.
The article is pointing out that:
1. Most ocean plastic enters the ocean from East Asia (80%)
2. Only about 5% of its enters the ocean from North America or Europe
3. But some plastic waste is exported form North America or Europe to Asia.
4. So is it plausible that the true waste share of NA and Europe is higher?
5. It concludes, yes, North America and Europe contribute as much as 5% of ocean plastic directly and then up to a further 5% via waste export.
It doesn't contradict itself, your parent poster didn't "just pick a random sentence from the article," and you should maybe read more carefully.