postage due stamp

17 LETTERS · STARTS WITH P

postage due stamp is a valid 17-letter word worth 23 points in Scrabble and 28 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

P3O1S1T1A1G2E1D2U1E1S1T1A1M3P3

3 + 1 + 1 + 1 + 1 + 2 + 1 + 0 + 2 + 1 + 1 + 0 + 1 + 1 + 1 + 3 + 3 =23 PTS

DOUBLE WORD → 46TRIPLE WORD → 69

MEANING

What does postage due stamp mean?