PLEASE HELP WITH TU REPORTING AUTHORIZED ACCOUNT

[senseidab]

I recently was added to a parents AMEX account as a AU.   TransUnion crdeit report is reporting the 20,000 extra credit limit.  But it is rerporting me as an AU with the account opened 12/16 and not giving me the benefit of the primaries card holder history going back to 2008    it reporting history from 12/16 forward.  Does this make any sense?   Do all three bureaus so the same in requards to reporting the history of the account.

also, why does my FICO  not add these AU credit limits to your overall credit available ( in other words) they dont count the AU credit limit into the utilization calculaton.

Can anyone help  please.       TY 

[takeshi74]

That's how AmEx reports for AU's.

Tradelines where one is an AU are not always considered by scoring model and/or creditor.  It depends on the model or creditor and the specifics of one's siutation.  FICO has some method of preventing piggybacking in certain situations but has not disclosed the details on how they determine this.