Check this site. It appears the ARINC coding is incorrect, at UKBB/KPB, the mistake is that the TR NDB is coded as IF, not a TF leg.
Here is a low cost explanation of RNP and ANP....
from
737.org
Actual Navigation Performance (ANP) is the FMC's estimate of the quality of its position determination. The FMC is 95% certain the the aircraft's actual position lies within a circle of radius ANP centred on the FMC position. Therefore the lower the ANP, the more confident the FMC is of its position estimate.
Required Navigation Performance (RNP) is the desired limit of navigational accuracy and is specified by the kind of airspace you are in. Eg for BRNAV above FL150, RNP=2.00nm. The RNP may be overwritten by crew.
ACTUAL should always be less than RNP.