Quick question about Arreat Summit's info

[Vash]

What does the number in the brackets above the blocking percentage mean on shields, shrunken heads, and paladin shields?

[Ruvanal]

That is the base blocking of the shield before the character class blocking amount is added. (Pal: 30%, Ama/Asn/Bar: 25%, Dru/Nec/Sor: 20%).

You would then need to use the total in the blocking formula.