It's hard for me to explain well but I count in a different way than others do. I did start writing in 2016, and if you are counting in the most common sense type of way 2016-2024 would be 8 years because from 2016-2017 is one year. However, when I count, I count 2016 as one year individually until 2024 which is why I got 9 because I counted 2016 when i wasn't supposed to.

No one really corrected me on how I count at all because in my head it made sense and was easier to understand until I brought your question up to my parents and they told me no, so thank you!