03 numbers of increment in a year

Dear Members, please clarify/post your suggestions/provide specific copy of orders if any on the following case-
In my office [District Registrar, Uttar Dinajpur, under department of Finance (Revenue), Government of West Bengal] the post of few Lower Division Clerks confirmed in a year and subsequently, were promoted to the post of Upper Division Clerk in the same year (e.g. 2010). Providentially, 02 (two) Upper Division Clerks are promoted to the post of Head Clerk in the same year (e.g. 2010). They were allowed to get promotional increment in each step of promotion too within the year of their promotions e.g. 1st promotional increment at the time of their promotion to the post of Upper Division Clerk, 2nd increment allowed as annual increment, 3rd increment was given at the time of their promotion to the post of Head Clerk in the same year i.e. within a year. I have found in a book written by Pashupati Ghosh, where it is described unjustified, a person must hold his or her post minimum one year after 1st promotion and before 2nd promotion.