The basicity of tetraoxusulphate 6 acid is 6. Explain that statement with an equation and show the reaction between the acid and potassium hydroxide

The reaction is H2SO4 + 2KOH ==> K2SO4 + 2H2O

I have no idea what a basicity of 6 means . The basicity of H2SO4 is 2 in my book.