weighted gpa

okay my school is out of a 4.5 scale and give you a gpa and give a certain point value for the grade and what type of class like ap, honors, or regular. they give you your gpa already weighted. but i was wondering is this the gpa they give me the right gpa. i see lots of kids having 3.5 unweighted and having like 4.3 weighted how is this possible? is there another way to calculate weighted like i herd someone tell me you add 1 for every ap you have to your gpa. but if my school already gives me weighted do i still had .1 for ap or do i add .1 to unweighted or the one my school gives me is the right one and stop worrying
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<p>every school does it differently, but usually for MOST schools, APs count as extra credit on your GPA and will boost it higher than the traditional 4.0.</p>