matter-of-factly

Who's afraid of Virginia Woolf?は戯曲なのでト書きがあり、そのト書きに書かれている単語や表現に普段余り見掛けない表現に出会います。
MARTHA: ... before I'm through with you you'll wish you'd died in that automobile, you bastard.
GEORGE [emphasizing with his forefinger]: And you'll wish you'd never mentioned our son!
MARTHA [dripping contempt]: You ...
GEORGE: Now, I said I warned you.
MARTHA: I'm impressed.
GEORGE: I warned you not to go too far.
MARTHA: I'm just begining.
GEORGE [calmly, matter-of-factly]: I'm numbed enough ...
[dripping contempt]の "dripping" も良く分かりませんが、それはとりあえず無視して、 [calmly, matter-of-factly]:の "matter-of-factly" が気になるので調べます。
「実は」の様な前置きとして "as a matter of fact" と言いますが、その副詞形の様な "matter-of-factly" の意味は辞書に載っているか調べます。
・Wiktionary: 1. As though stating a fact: "I took the liberty of inviting somebody else to have dinner with us," Stallman said, matter-of-factly, giving me the same cat-like smile he gave me back in that Palo Alto restaurant. 2, As though the situation is normal and not unusual; not dramatically or fancifully.: He was not of the East; and he came of a breed who fought devils and wizards as promptly and matter-of-factly as they battled human foes.
多くの辞書は "matter-of-factly" は"matter-of-fact" の副詞形として後者の意味だけを次ぎのように説明しています。
・Cambridge English Dictionary: not showing feelings or emotion, especially in a situation when emotion would be expected: He spoke in a very matter-of-fact way about the accident.