CC1312R: how to determine cap-array delta when tuning HF crystal?

Hi,

We are trying to migrate a CC13-90 based design to CC1312R from CC1310. Unfortunately,  the current design doesn't include load capacitors for HF crystal. My understanding is that we can turn on internal cap-array to compensate. My question is, what does the Cap-Array Delta mean in Smart RF Studio/Syscfg? What is the unit? How do we determine what value to use?

I assume we can connect the board to a spectrum analyzer and do a trial-error, but that seems quite inefficient.

Thanks,

ZL