Antigone 925-929

[Bart]

Question about particles. Antigone's last speech:

ἀλλ᾽ εἰ μὲν οὖν τάδ᾽ ἐστὶν ἐν θεοῖς καλά,
παθόντες ἂν ξυγγνοῖμεν ἡμαρτηκότες:
εἰ δ᾽ οἵδ᾽ ἁμαρτάνουσι, μὴ πλείω κακὰ
πάθοιεν ἢ καὶ δρῶσιν ἐκδίκως ἐμέ.

If the gods approve of what is happening, then by suffering (i.e. after I die) I will come to realize my mistake; but if it is these (people) who are in error, may they suffer no worse than the injustice they are in fact doing to me! (translation by Mark Griffith).

Griffith states that the introductory particles make clear that the two alternatives offered in these lines are not of equal plausibility, writing that μὲν οὖν "emphasizes the prospect of a more probable sequel (here εἰ δ᾽)."

So, there are two alternatives
1) εἰ μὲν οὖν Antigone is wrong
2) εἰ δ᾽ these people are wrong

Surely Antigone thinks that alternative 2 is more plausible. And this is what Griffith appears to be saying. But in what way does μὲν οὖν (introducing the first alternative) signal this?