DS90UB954-Q1: Parity Error counter and BIST Error counter values don't match

Hello,

BIST was performed and checked Parity Error counter and BIST Error counter however values don't match.

for example.  Parity errors seen but no BIST error seen 

in other timing, parity error wasn't seen but BIST error seen.

I Thought when parity error is seen the BIST error is also seen. why this happens?