It's an idiomatic use of the verb "acabar": http://www.semantica-portuguese.com/acabar-de-conjugation-21196/
The preterit of "acabar de" + infinitive = have just + past participle.
Eu acabei de receber a resposta dela.
I have just received her answer.
To refer to an action from a past perspective, use the past perfect of "acabar de".
Eu tinha acabado de receber a resposta dela antes de sair do escritório.
I had just received her answer before I left the office.
Modern Brazilian Portuguese Grammar - Whitlam
Both you and a commenter on this post (from Davu http://www.semantica-portuguese.com/acabar-de-conjugation-21196/) use the conjugation eu tinha, what is the difference between that and eu tive? Both appear to be correct grammar... Is this "I have" vs. "I had"?
Acabar de + infinitive = has/have just + past participle