Hola Shirley

I imagine you are referring to this quiz:

"Hoy no he quedado con nadie" means

I am not meeting anyone today.

Quedar in this context means "to meet" or "to arrange to meet" as explained in this same threat (scroll down to see answers) The translation given to this sentence: "I am not meeting anyone today" is the same as saying "I haven't arranged to meet anyone today". We used what we thought was more natural, although it requires a different tense.

I hope this helps.

Saludos

Inma