The ACT reports four section scores (English, Math, Reading, Science), each 1-36, and the composite is simply their average rounded to the nearest whole number.
Because it's an average, a weak section drags the composite as much as a strong one lifts it — so raising your lowest section is usually the fastest composite gain.
Each section's raw-to-scaled conversion shifts slightly by test date, so a projection models the curve rather than a fixed point count.
Try it: ExamScoreCalc on act composite built.