" The proviso to sub rule (2) of rule 12 was again substituted by the following proviso with effect from February 23, 1978: "Provided further that if any person appointed to the Section officers ' Grade is considered for promotion to Grade I under this sub rule, all persons senior to him in Section Officers ' Grade who have rendered not less than six years ' 152 approved service in that Grade, shall also be considered notwithstanding that they may not have rendered 10 years ' approved service in that Grade; provided that the aforesaid condition of six years ' approved service shall not apply to a person belonging to the Scheduled Castes or the Scheduled Tribes." Thus according to this proviso to sub rule (2) of rule 12 a direct recruit Section officer who has rendered six years ' approved service in that grade was eligible for consideration for promotion to Grade I whereas a promotee Section officer would have to render ten years ' approved service in the grade of Section officer before being eligible for consideration for promotion.