Lined paper, B5
Seven millimeter ruling on B5, which is close to what most Asian school notebooks use.
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Ruling width and handwriting size
Seven millimeters suits adult handwriting and is roughly what Japanese and Korean B5 notebooks use. European A4 pads tend to run 7 or 8 mm, US college ruled is about 7.1 mm and wide ruled about 8.7 mm. If your writing is large, go up rather than writing smaller, because notes you cannot read back quickly have failed at the only thing they are for.
Check ISO against JIS before printing inserts
ISO B5, used here, is 176 by 250 mm. JIS B5, used by Japanese notebook brands, is 182 by 257 mm. For loose sheets the difference does not matter. For inserts meant to sit inside a specific notebook it does, and the fix is to measure the actual page and enter it as a custom size in the generator rather than trusting the label on the cover.
Margins for bound versus loose
A loose sheet wants an even margin. A sheet going into a bound notebook or a ring binder wants a wider inner margin, because the gutter swallows the inner edge and any ruling that runs into the binding is ruling you cannot write on. Add at least 20 mm on the bound edge, and more if the notebook does not lie flat.
Printing it accurately
This only measures correctly if your printer doesn't rescale the page. In the print dialog set Scale: 100%, not "Fit to page" or "Shrink oversized pages". If you're not sure it worked, print the calibration page, measure the ruler on it with a real ruler, and it will tell you exactly what your printer is doing to the page.