(b)
The number of officers that a board convened under section
251 of this title may recommend for promotion to a grade below rear admiral (lower half) from among eligible officers junior in rank to the junior officer in the appropriate promotion zone may not exceed—
(1)
5 percent of the total number of officers that the board is authorized to recommend for promotion to the grade of lieutenant or lieutenant commander;
(2)
71/2 percent of the total number of officers that the board is authorized to recommend for promotion to the grade of commander; and
(3)
10 percent of the total number of officers that the board is authorized to recommend for promotion to the grade of captain;
unless such percentage is a number less than one, in which case the board may recommend one such officer for promotion.