Let \(\mathcal {S}_p\big (A^2(\Omega )\big )\) denote the Schatten p-class of the Bergman space \(A^2(\Omega )\) on a smoothly bounded strongly pseudoconvex domain \(\Omega \subset \mathbb {C}^n\) . This paper shows that if \(\begin{aligned} {\left\{ \begin{array}{ll}\tau =0\ & \ \ \text {as}\ \ p\in \left( \frac{2n}{n+1},\infty \right) ;\\ \tau >\left( \frac{n+1}{2p}\right) \left( \frac{2n}{n+1}-p\right) \ & \ \ \text {as}\ \ p\in \left( 0,\frac{2n}{n+1}\right] , \end{array}\right. } \end{aligned}\) then \(C_{\varphi }\) belongs to \(\mathcal {S}_p\big (A^2(\Omega )\big )\) if and only if \(\begin{aligned} \left( \int _\Omega \left( \left( \delta (z)\right) ^{n+1+2\tau }\int _\Omega \left| K_\tau \left( z,\varphi (w)\right) \right| ^2\textrm{d}v(w)\right) ^\frac{p}{2} K(z,z)\textrm{d}v(z)\right) ^\frac{1}{p}<\infty . \end{aligned}\) This result extends [13, Theorem 1.1] from the range \(p > \frac{2n}{n+1}\) (the previously known case) to \(p \le \frac{2n}{n+1}\) (which was an open problem).