What is Mastery of reflectionJhana mastery

They say to master jhana you must master five factors. I understand the first four but mastery of reflection is kind of leaving me unsure. I think i get it. Once you come out of the jhana state, you refect on the absorption factors like you do the jhana factors you focus on each until the hindrances is gone. But what are these absotbtion factors. Do i just think about it or stsrt a second meditations on each factor and be aware of them? How do i know what these factors are and distinguish them? They also say there different absorption factor to reflect on. Can you help me understand