Age allowance (f6)

please i need clarification on age related allowance. Normally all age allowance shouldn’t go below personal allowance when being adjusted in case the net income exceed income limit, according to what i read. but i saw an example in BBP where the adjusted age related allowance is $8,055 after deducting half excess from age related allowance but still being used ($8,055) instead of $8,105. check page 23 under age allowance example (BBP Study text). Your response will be appreciated.

cheers