Hello and thank you for your help.
I was checking the datafile to understand your logic.
Indeed, the aircraft 3317/16 has the w / n 427 but I have a worry because on page 6 of the datafile, they show the plane 4982/16 and they say that the w / n is 622.
It is part of the series starting with 4800/16 and ending in 5039/16, which would mean that for the aircraft 4800/16 the w / n is 440??
I do not understand anything, if you can enlighten me

.
Thank you in advance,
Samuel.