Please answer a question about the following article about Alsace:

The constitution of the Fifth Republic states that French alone is the official language of the Republic. However, Alsatian, along with other regional languages, are recognized by the French government in the official list of languages of France. A 1999 INSEE survey counted 548,000 adult speakers of Alsatian in France, making it the second most-spoken regional language in the country (after Occitan). Like all regional languages in France, however, the transmission of Alsatian is on the decline. While 39% of the adult population of Alsace speaks Alsatian, only one in four children speaks it, and only one in ten children uses it regularly.

How many adult speakers speak Alsatian according the 1999 INSEE survey?
548,000