One of the major aim of any theoretical calculation is to simulate experimental results. The possible sources of error for the K-edge core ionization in the SS-FNO-IP-EOM-CCSD* method are the finite basis set effect, the residual correlation effect, the relativistic effect, and the vibrational effect. The finite basis set effect is the easiest to take care of in most cases. Table demonstrates the comparison of results between the SS-FNO-IP-EOM-CCSD* method and experimental results for the Cheng test set, using uncontracted aug-cc-pCVXZ (X=D, T, Q) and uncontracted 6-311++g** basis sets. The improved accuracy of the core-ionization energy with respect to the experimental value can be observed when transitioning from the unc-aug-cc-pCVDZ to the unc-aug-cc-pCVTZ basis set.