Every door and window in a plan set subtracts studs from a wall and adds header framing back in — miss the opening schedule and your takeoff will run systematically high on field studs and low on headers, jack studs, and cripples.
What to pull from each opening
For each opening, you need:
The framing math
From there, the framing math follows directly: two king studs and two jack studs per opening, cripple studs calculated the same way as field studs but sized to the header-to-plate or sill-to-plate distance, and a header sized either from a span table (bearing walls) or a minimal standard (non-bearing partition walls).
The risk of skipping the schedule
Skipping the opening schedule and estimating from square footage or wall length alone is one of the fastest ways to blow a stud count in either direction — over-counting field studs where openings should have subtracted them, and under-counting the opening-specific framing that a plain wall length doesn't capture at all.