Interval between two meditation sessions-
After finishing one session in which meditation on one substance or mode is undertaken and before starting another session in which meditation on another substance or mode would be undertaken, during the intermediate period the practitioner undertakes reflection or Anuprekṣā (4) (contemplative meditation) about the latter one.
'jhāṇaṃtariyāe' tti antarasya - vicchedasya karaṇamantarikā......dhyānāntarikā.
(Bhaga 5.86 Vṛ)
annatarajjhāṇa'tīto, biiyaṃ jhāṇaṃ tu so asaṃpatto.
jhāṇaṃtarammi vaṭṭai, bipahe va vikuṃciyamaīo...
(BṛBhū 1643)