Service matter

i have been approached by an officer of PSU Bank regarding fixation of pension and terminal benefits. the detail of the case is as below: 1.he is serving his organisation for last 32 years 2. He was promoted from scale I to scale ii in year 2010. 3. He served in scale ii for 30 months and was subsequently demoted to scale i. 4.in 2016 he was again promoted to scale ii and is due to retire in few months. 5.he has approached the management for consideration of his prior service in higher scale while deciding upon terminal benefits,which was subsequently turned down by the management. what is legal view point on this matter? should his prior service has to be taken in consideration while deciding upon his terminal benefits?