Integrate[Sinc[x],x]

g[t_,v_]:=Integrate[Sinc[x-v],{x,t,t+3^(-4)}]

g[0,0]

N[SinIntegral[(1/81)]]

h[t_]:=Integrate[g[t,v],{v,t,t+3^(-4)}]

N[h[1006]]

Clear[h]

N[3^(-8)*Sinc[0]]