These are fixed thresholds built-in to the chip for thermal protection. The present chip temperature (die temperature) is tracked in the TDIE_VALUE register, which is updated periodically during chip operation.
TJOFF (165degC) - Beyond this temperature the chip will shut down to prevent chip failure.
TJWARN (120degC) - At this temperature the chip will warn the user that it is operating at a temperature higher than typical operating temperatures. Based on this the user can configure the chip, for example, stop charging or reduce charging current.