pK₁ and pK₂ of H₂CO₃ are respectively 6.38 and 10.26. pH of 1 M and 0.1 M NaHCO₃ respectively are

H₂​CO_3​+H₂​O⇌HCO₃^−​+H₃​O⁺; pK₁​=6.38
HCO₃^−​+H_2​O⇌CO₃^2−​+H₃​O⁺; pK₂​=10.26

${\mathrm{HCO}}_3^{-}$ is proton acceptor as well as proton donor and therefore it is amphiprotic,

$\mathrm{pH}=\frac{{\mathrm{pK}}_1+{\mathrm{pK}}_2}{2}=8.32$

As pH in indendepndent of concentration, therefore value of both 1 M and 0.1 M NaHCO₃ is 8.32.