piano chord
D♭maj9
D♭1F3A♭5C7E♭9
A major seventh with a ninth on top.
Written the other way round it is C♯maj9 — the same twelve keys on a piano, a different piece of notation.
What is true of it
D♭maj9 is D♭, F, A♭, C and E♭ — 1, 3, 5, 7 and 9 counted from D♭.
On an instrument that cannot reach all 5, the 5 and 1 go first, in that order.