Time machine Backup/restore from OSx 10.10 to 10.13

Hi Guys,

I had a Macbook air with 10.10, took backup from Time machine & was suppose to restore with a New Mac air which is running with 10.13 HighSierra. A complete data of 120GB was backed up on time machine with an average of 5-6hrs & restored on New Macbook air. It was Successfully completed with Migration Assistance facing no errors. But then when I look into individual data, few files of around 100mb of excel/word data were missing from old mac to new mac and rest all files/folders/category was unchanged. I was wondering what could be the reason for that & could any one help me out with technical reason.