The formula of deecibel calibration

[Jens Noriʇzsɔɥ]

Does that mean that even if I know the SPL correction value for multiple data, I cannot compare those data?

Hm, I am not sure that I understand your question, sorry.

You cannot expect that the offset is identical for different devices. Once calibrated, you should obtain reliable results with this one smartphone – within the limitations of the imperfect audio hardware.

Simple comparisons should always work: louder stays louder regardless of the offset. If your audio signal stays in a rather small frequency band, SPL differences should be even quite ok (no offset needed here).