In chapter XII of the 2003 edition of Lingua latina per se illustrata, one can read the following sentence (lines 93-94):
Aemilius in castrīs habitat mīlle passūs ā fīne imperīi.
I understand its meaning, but I can't figure out the grammatical role of "mīlle passūs". Since "habito" is a transitive verb, should "mīlle passūs" be interpreted as the direct object for such verb? I.e., is "passus" in accusative plural case?