'Royal' in the Bible

Rehum the royal officer and Shimshai the scribe wrote a letter against Jerusalem to King Artaxerxes as follows

(then Rehum the royal officer, Shimshai the scribe, and the rest of their associates, the judges, the envoys, the officials, the Persians, the Erechs, the Babylonians, the Susians (that is the Elamites)

Now be it known to the king that if this city is built and the walls are finished, they will not pay tribute and toll, and the royal revenue will be reduced.

The king sent a reply: "To Rehum the royal officer, Shimshai the scribe, and the rest of their associates who live in Samaria and the rest [of the province] Beyond the River, greetings. And now