After Appendix A’s first subsection presented us with a “sink or swim” bombardment of information, this subsection is rather light.
“The Realms in Exile” is essentially a genealogy of the two branches of the heirs of Isildur. Tolkien has listed them simply as the Northern Line and the Southern Line. For further stability in our minds, Tolkien starts each line with Elendil and Isildur. From there, each successive heir is listed alongside the final year of their reign, mostly in the Third Age. Likewise, both lines are unified at the end with Aragorn II / Elessar Telcontar in Fourth Age 120.
The Southern Line, which includes the Kings of Gondor, also lists the reign of the Stewards of Gondor from the House of Húrin, into the Ruling Stewards beginning with Mardil through 2080, and finalizing with Faramir, Lord of Emyn Arnen through Fourth Age 82.
This list will be expanded upon in story in the next subsection.