I took 3 courses in 2017 (Sep-Dec) and was given 3 months Part-Time credit on the T2202A. I also took 3 courses in 2018 (Sep-Dec) but was given 4 months credit on T2202A?

In 2017 I had taken 3 courses for one of the semesters and the T2202A showed I had 3 months of Part-Time (September to December). In 2018 I also took 3 courses for each semester but both semesters show 4 months of Part-Time (January to April, September to December). Why does my 2017 T2202A show 3 months while the 2018 T2202A shows 4 months for the exact same period (September to December)? Is this something I should ask my University to fix or is it not worth looking into?