The phrase "first modification" refers to the initial change or alteration made to something. It suggests that there may be subsequent modifications or changes after the first one. Full definition
The first modification to Pastor Bonus, the 1988 pastoral constitution that regulates the functions and tasks of the offices of the Roman Curia, came on July 9 with the transfer of the ordinary section of the Administration for the Patrimony of the Apostolic See (APSA) to the Secretariat for Economy. (faith.org.uk)
Without doubt the first modification is to fit new track - biased tyres. (evo.co.uk)
L15A1 was the first modification with a 16 - valve SOHC VTEC head. (mywikimotors.com)