Question about RCPHASE

Register 14:04 RCPHASE

noted in user manual:
This 7-bit field reports the receive carrier phase adjustment at time the ranging timestamp is
made. This gives the phase (7 bits = 360 degrees) of the internal carrier tracking loop at the
time that the RX timestamp is received. This can be used to partially compensate for the
phase offset in the CIR’s between two DW1000 devices.
what exactly does this mean?

suppose local carrier is denoted as:
and signal recieved is denoted as:

is RCPHASE = phi2 - phi1?