Answer
$\Delta G^{\circ}$ is constant and $\Delta G$ varies with concentration.
Work Step by Step
$\Delta G^{\circ}$ is constant value as it does not depend on concentration, that is why there is a specific number. $\Delta G$ is a range because it varies with concentration of reactants like ATP and products like ADP and $P_{i}$, and $\Delta G^{\circ}$. Thus, it is given in a range and not a precise number.
