Anicca: Impermanence
Anicca is the passing nature of anything that arises. Smoke is the sharper of the two images: it holds a shape for a moment over the fire, then there is nothing left to point at, and the whole sky is handed that same ending. The earth beneath goes at the slower pace, a coat thinning at the elbows year by year, which is why the eyes have to be lifted on purpose to catch what is already underway.
Saṅkhāra: Things put together
Saṅkhāra is whatever has been assembled out of parts. A garment is the plain case: thread, dye, stitching, and it fails along the very seams where it was made. Heavens and earth come under the same description, so their ending follows from their making, and nothing has to go wrong for smoke to thin out; it only has to keep being smoke.
Jarāmaraṇa: Aging and death
Jarāmaraṇa is the wearing down and the ending that close a life. The cloth wears out and the wearer dies, both said in one breath, since a single process runs through the coat and through the person inside it. "Its inhabitants will die in the same way" turns the picture back on the listener: whoever is lifting their eyes is standing among the things that wear out.
Saṃvega: Urgency at seeing how things stand
Saṃvega is the jolt that becomes urgency. Lift up your eyes is an order, spoken to exiles who had already watched their city fall, so the jolt is expected to land and then move them. Anyone who has seen a house burn needs no telling that smoke does not last; raising the eyes is meant to let that plain fact rearrange what the remaining days are spent on.
Asaṅkhata: The unmade
Asaṅkhata is what was never put together and so cannot come apart. Salvation forever and righteousness that will not be abolished arrive at exactly the point where sky and earth have just failed, offered as a different kind of thing, not a sturdier one. The eyes were lifted to the heavens and found smoke there, so whatever holds stands outside everything the eyes can sweep.