备注:This standard includes specifications for hexagon head flange screws with a flange Ф that is ≈ 2 × the size of the nominal thread 0, as convex screws (first seat of transitional arc-runout) with metric coarse threads from M5 to M10 and metric fine-pitch threads from M12×1.5 to M16 ×1.5 in product class A.括弧中的内容是什么意思?