τεκμήριον δὲ μέγιστον τοῦ εἶναι ταῦτα σημαντικὰ φησιν ὅτι ἔχοντά τινος ἐννοιαν πεπλασμένην (οἷον ἄρα γε τί ποιεῖ Σωκράτης, καὶ ἀκούσει τινὸς ὅτι ἐξηγεῖται ἣ καθέζεται ἣ βαδίζει) ἕστησεν τὴν σεσαλευμένην καὶ πεπλανημένην διάνοιαν, καὶ αὐτὸς ὁ ἀκούσας ἠρέμησεν.
He said that the biggest proof of nouns being significant is the fact that the hearer, upon hearing the nouns having a formed thought about something (for instance, ‘what does Socrates do?’ and hearing from someone that he is leading, sitting or walking) stops the vacillation and wandering of his process of thinking and himself acquiesces.
I hope this is correct and the acc in ἔχοντά τινος ἐννοιαν πεπλασμένην refers to ταῦτα σημαντικὰ that is the nouns.