Adhyaya 8

It states that Alarka alone, as a youth, ruled (and ‘enjoyed’) the earth for sixty thousand years plus six hundred, without another rival claimant to sovereignty.

As Purāṇic historiography: such durations function as markers of extraordinary karmic fruition and narrative emphasis, set within cosmic time (kāla) governed by Viṣṇu, rather than as ordinary human chronology.