Promotion

sir, I have been working as a Tax Assistant in CBIC for 4 more than 4 years and currently posted in Mumbai Customs. I have also cleared confirmation exam for the same. In another exam i got selected as Tax Assistant in CBIC again and have been allotted Lucknow GST (my hometown). I am planning to take technical resignation and join Lucknow GST. DOPT has issued an office memorandum vide F. NO. No. 28020/2/2018-Estt.(C) dated 27/08/2020 regarding techical resignation. My question is whether my old service, 4 years, should be counted at the time of promotion, since both appointments are same and in same board, department and ministry. Thanking you in anticipation.