The first paragraph used figures from Eurostat, the statistical agency of the EU. In 2017, this source took estimates for trade within the EU into account for the international trade of the Netherlands for the first time.
The Dutch statistical agency CBS has been doing this for a while now. Of the larger companies, the CBS registers the actual international trade, but of smaller companies, this trade is estimated. The declaration threshold of intra-trade is 1.2 million euro for export and 1.0 million euro for import.
Another important difference between Eurostat and CBS is that the Eurostat figures also take quasi-re-export into account, and the CBS figures don’t.