538 The Accusative of a noun of time or space may denote extent:

Ἔμεινε τρεῖς ἡμέρᾱς he remained three days. ἔτη γεγονὼς ἑβδομήκοντα seventy years old. AP. 17 d. πολὺν χρόνον ἠπόρουν I was in doubt a long time. AP. 21 b.

Ἐξελαύνει σταθμὸν ἕνα παρασάγγᾱς ὀκτώ he marches one dayʼs journey, eight parasangs. ἀπεῖχον τῆς Ἑλλάδος οὐ μεῖον ἢ μρια στάδια they were not less than ten thousand stades distant from Greece. AN. III. 1, 2.