How should the time spent in a pay grade be accounted for when a teacher, covered by the special service time recovery scheme, is simultaneously entitled, in that pay grade, to the bonus provided for in points a)/b) of paragraph 1 of article 48 of the ECD (for merit mention in the previous pay grade) and to the reduction provided for in paragraph 1/2 of article 54 of the ECD (for obtaining a master's/doctoral degree)?