Some colleges take your gpa off the transcript. Some recalc.
If you used no ±, you’d have
18 points for year on 5 classes
16 points on 5 classes 2nd year
16 points on 4 in 11th.
So 50/14 =3.571
Now some may not count 9th. Some may do a +.33 or -.33 for +/- but it wouldn’t make you a 3.1.
Ask the college that have you a 3.1 how they calculated it. You want to ensure they have the right # for merit.
Glad they accepted you. Congrats.