Credit went from Nil to Excellent... can this be real?

[Lance Luvaul]

Hi all, I just want a sanity check from the BP folks here.

I just asked my dad to add me as an authorized user to one of his credit accounts in the US to help me rebuild my credit scores there (since I closed all my accounts 10 years ago when I moved overseas).  I just created an account with Credit Karma so I can keep an eye on my score's growth as I take additional steps to improve it.  But already I see it has gone from nothing to excellent with the addition of my father's credit account history!

My question is, is this real or some artifact of the algorithm Credit Karma use to compute the scores?  How accurate are Credit Karma results?

Sounds too good to be true...