रात्रिभागौ द्वौ स्वप्नकाला त्रिभागः संवेशनोत्थानिकः ॥ कZ_०२.३१.०७ ॥
rātribhāgau dvau svapna-kālā tribhāgaḥ saṃveśana-utthānikaḥ
Two divisions of the night are for sleep; the third division is for settling down and rousing (night handling/guarded management).
It implies planned night supervision—checks, repositioning, readiness to respond to disturbances—rather than leaving valuable assets unattended.