First before breaking down the lyrics, if you don't know the meaning of some terms:
KOSMO
In its most general sense, a cosmos is an orderly or harmonious system. It originates from the Greek term κόσμος meaning "ordered world" and is the antithetical concept of chaos. Today the word is generally used as a synonym of the word Universe (considered in its orderly aspect).
Kozmo in Aespa's dictionary is the final destination universe.
KWANGYA
광야, Gwang-ya is a word in Korean meaning "wilderness". Wilderness means the wilds, waste, jungle, or desert.
It was described as a place out of order which is the opposite of KOSMO.
The FLAT
It's the place where the AEs came from and where Naevis control the ports from.
P.O.S
The Port of the soul is the gate/portal that the alter egos and real people go through to different universes.
SYNK
When the digital alter ego and the real self sync.
The song is during their journey to the other side and it's about their target.
Lyrics and their meaning:
i'm down 
