It depends which number is off.
Gross pay should match. It's contract math — what the agreement says you're owed for the times you entered, against what payroll actually processed. When the two differ, the Summary breakdown shows which line accounts for the gap: a meal penalty that wasn't paid, overtime that started an hour late, a distant day treated as local. That's a far easier conversation with your UPM or payroll coordinator than “this looks low.”
Net pay is an estimate — usually within a few percent of the real check, because withholding depends on details your times don't show. If the gap is bigger than that, start with the three that move it most: the contract and subtype, your work and hire states, and your filing status and allowances. Then grace and meal settings, local versus distant hire, any rate overrides from a deal memo, and mileage, per diem, and box rental, which are paid to you but taxed differently from wages.
Some things it can't see at all: garnishments, a loan-out you haven't set up, 401(k) or benefit deductions, and a production's own accounting adjustments.