Rules of the Road: INTERNATIONAL ONLY Two power-driven vessels are crossing within one half mile of...

International ONLY
Rule 34 - Maneuvering and Warning Signals
(a) When vessels are in sight of one another, a power-driven vessel underway, when maneuvering as authorized or required by these Rules, shall indicate that maneuver by the following signals on her whistle:

(i) one short blast to mean "I am altering my course to starboard";
(ii) two short blasts to mean "I am altering my course to port";
(iii) three short blasts to mean "I am operating astern propulsion

If A altars its course starboard, wouldn't that mean that they would be leaving vessel B on their Port?

International and Inland are different. International is shown below. Inland is
(i) shall indicate that maneuver by the following signals on her whistle: one short blast to mean “I intend to leave you on my port side”; two short blasts to mean “I intend to leave you on my starboard side”; and three short blasts to mean “I am operating astern propulsion”.

(i) one short blast to mean "I am altering my course to starboard";
(ii) two short blasts to mean "I am altering my course to port";
(iii) three short blasts to mean "I am operating astern propulsion