The present perfect connects the past to the present. The example you gave describes one such possible context. Another would be a present result of a past action:
e.g.,
A: Would you care for a sandwich?
B: No, thanks. I've (already) had my dinner.
The present perfect connects the past to the present. The example you gave describes one such possible context. Another would be a present result of a past action:
e.g.,
A: Would you care for a sandwich?
B: No, thanks. I've (already) had my dinner.
It could mean that. In fact, if you tell somebody you're not hungry because you have already eaten that in itself indicates how recently you might have eaten.
It means that there is a connection to now. With the example of dinner, it is likely to be fairly recent because we have dinner every day. However, if you say that you have eaten in a restaurant, it does not necessarily mean that it was very recent.