Armor Penetration and Armor resistance.

[Dan Howard]

The only evidence we have for Greek linen armour suggests that it was around 15 layers not 30. Medieval jacks could be up to 30 layers thick. In any case properly cast and work hardened bronze is far superior to all but the best quench hardened steels. It would have been well within the capability of a bronze age smith to make a bronze needle capable of sewing 30 layers of fine linen.