19.4.8 WDT Period Selection
The Sleep mode counter always uses the 32 kHz LPRC clock source. The Run mode counter uses the clock source selected by the DEVCFG2.WDTRMCS[1:0] Configuration Bits in fuses to be either the 32 kHz LPRC clock or the SYS_CLK.
Note: The WDT module time-out period is directly related to the frequency of the LPRC Oscillator when clock source is 32 kHz LPRC. The frequency of the LPRC Oscillator varies as a function of the device operating voltage and temperature. See Electrical Characteristics from Related Links for LPRC clock frequency specifications.