Eleanor, I would take it as a strong clue that your paternal surname is ROCK. About 1/2 of your autosomal DNA Match are probably on his side and half on your maternal side. You will match others with a blood (biological) relationship – that’s the path the DNA follows. You should get not real matches with any foster parents (unless there is some distant blood relationship). When starting out with autosomal DNA, I would work with (contact and shareinfo with) your closest Matches first – they are the ones who are listed first.