Inter se seniority of direct recruits and promotees

I have joined one of Central Armed Police Force after being selected as Assistant Commandant in year 2011 against the UPSC CPF (AC)-08 exam. The recruitment process was started in year 2008 with notification of CPF(AC)-08 Exam by UPSC and the examination was conducted in year 2008. Susequently, physical & medical and interview was conducted in year 2009 and in the same year result was announced. But the appointment letter for joining were issued in Nov 2010 with Date of Joining on Jan 11 and, accordingly I joined in Jan 11. But I was available from year 2009 after completion of all recruitment formalities and due to some admnistrative reason, appointment letters issued after 14 months. In between, some inspectors of force get promoted to Assistant Commandant through regular promotion and LDCE exam and as they had already in service, they got promoted rank as soon as the department exam or DPC result announced. Consequently, they become senior to me, even those who get promotion in year 2010 as per department seniority list and I along with my batchmates put after their in seniority roster. Our department considered date of appointment for decicding seniority roster. Hence, plz put some light on issue that where should we be placed in seniority roster and from which year our seniority should be counted in colloboration with recent DoPT OM. Thanks.