On page 44 of the datasheet, they have given the formula to calculate the crystal load capacitance.
I have a crystal. It's datasheet mentions that it's load capacitance is 6pF and Shunt capacitance is 3pF.
And considering 3pF for CB1 and Cxtal of 6pF (mentioned in the pin capacitance table), CS1 = 3pf + 6pf = 9pf.
If I substitute CS1 in the formula,
C1 = 2*(CL - Co) - CS1
CL = 6pf
Co = 5pf
C1 = 2*(6pf - 5pf) - 9pf
C1 = 2pf - 9pf
C1 = -7pf
I am getting negative capacitor values for the load capacitances.
C0 is usually included (subtracted by the crystal manufacturer) in the specification for C L and should be set to 0 for use in the calculation of the capacitance formula
Load capacitance should be selected for typical rather than maximal external capacitance values to achieve best frequency matching.
As stated, shunt capacitance will be usually ignored in load capacitance calculation because it's already included in the specified target load capacitance.