Use the sheet manufacturer’s measurements
A4 is 210 by 297 millimeters, but label sheets have different margins, gaps, and grids. Enter the actual label width and height plus the top and left margins. The total grid must fit inside the paper: columns times label width plus gaps and margins cannot exceed the page width. Apply the same check to rows and page height.
Turn off automatic scaling
Choose A4 in the print dialog and use actual size or 100%. Disable fit-to-page, shrink-to-printable-area, and browser-added headers and footers. Even small scaling changes accumulate across a sheet. Prefer the downloaded PDF because it uses physical coordinates instead of a screenshot of the design canvas.
Calibrate on plain paper first
Print a test sheet on ordinary paper and hold it against the label stock. If the entire grid shifts uniformly, adjust the horizontal or vertical calibration offset. If the shift grows across the page, recheck scale, label pitch, gaps, and printer paper size rather than compensating with a single offset.