I see it @Shubhayan 
Your observation led me to this finding about - How Is Stoppage Time / Added Time / Injury Time Calculated
The referees take into account the following when adding time to the end of each half of football game:
- Substitutions
- Assessment of injured players
- Removal of injured players
- Time wasting
- Disciplinary sanctions being issued
- Any medical stoppages allowed by the rules, such as those for a drinks break
- Any delays added for VAR checks
Other causes deemed relevant by the referee, such as a streaker or excessive goal celebrations.
As each half of football approaches, the fourth official is tasked with displaying the minimum amount of time that the referee has told him will be added to the period. It is important to note that this is the minimum added time; a referee can decide to play more than the time indicated but not less than it.
It is said that the injury time isn’t a perfect science and the amount of time added onto a game can vary from referee to referee.
Looks like ISL coaches have been advised a fixed time addition for each of the above stoppage time falling in the broad categories with a certain levy of personal judgement. Most likely the referees are applying the given yardstick if the stoppages are falling in a specific category. Hence the 2" + 5".
The above is just my explanation to the recurring added time. I may be wrong.