The topic is about weight per CTN if the print label is 15 kg and the real ctn weight is 12 WHAT WE CAN DO DO MODIFICATION IN SELLER CENTER

hi i list my ist ptoduct in amazon fba in france my supplier from china he told me that weight per ctn is 15 kg and i printed the lable and supplier already send my ptoduct 2 days before now the real weight of per ctn is 12 kg what should i do now and also he did not pay custom duty if any one know please tell me i reall dont know what should i do now_emphasized text_