What is Admiralty Tide Tables or ATT and its volumes ?

On the back cover the map of the world showing the limits of each volume is drawn. Each volume is divided into three parts:

PART 1: Primary Ports ( Giving Daily Predictions Of Time Of Low And High Waters).

PART 2: Data Of Secondary Ports.

PART 3: Principle Of Harmonic Constants.

How Admiralty Tide Tables is corrected?

Correction of Admiralty Tide Tables is under SECTION:7 (MISCELLANEOUS PUBLICATION UPDATES) of weekly notice to mariners(WNTMs).

SHASHI RANJAN