By "selfish" I mean how each human (apparently) cares about himself more than others, which needs an explanation because there can't be a description of himself embedded in his brain at birth.

Pointing at self is possible, which looks like a reasonable description of self, referring to all the details of a particular person. That is, interpretation of individual's goal representation depends on the fact that the valued individual is collocated with the individual-as-agent.

Just as how a file offset value stored in memory of my computer won't be referring to the same data if used on (moved to) your computer that has different files; its usefulness depends on the fact that it's kept on the same computer; and it will continue to refer to same data if we move the whole computer around.

No, that's not the meaning I had in mind.

Now I'm confused again, as I don't see how these senses (one I suggested and one you explained in parent comment) differ, other than on the point of caring vs. not caring about counterfactual versions of same individual. You said, "each human (apparently) cares about himself more than others, which needs an explanation", and it reads to me as asking how can humans have the individual-focused utility I suggested, that you then characterized as not the meaning you had in mind...