I actually failed the test (by one point) but the teacher gave me a bonus point so I could pass.
I failed the test by just one point but the teacher kindly gave me a pass.
「不合格なんだけど先生がおまけで合格にしてくれた。」= I actually failed the test (by one point) but the teacher gave me a bonus point so I could pass. / I failed the test by just one point but the teacher kindly gave me a pass.
ボキャブラリー
actually = 実は、実際に
failed = 落ちた、不合格
test, exam = テスト、試験
by one point = 1点で
but = だけど
the teacher = 先生、講師
gave = 与えた、くれた
a bonus point = おまけて1点
so = ~するように
could pass = 合格できる
kindly = 優しく
a pass = 合格