20 stamps/page * 5 pages. You got 100 stamps in total.
Background: The long-running series celebrating American lighthouses continues with five new stamps. The mid-Atlantic lighthouses featured in this issuance are: Thomas Point Shoal, MD; Montauk Point, NY; Harbor of Refuge, DE; Navesink, NJ; and Erie Harbor Pierhead, PA. The late Howard Koslow was the artist for these stamps as well as previous issuances in the Lighthouse series. Mid-Atlantic Lighthouses were the last stamps he illustrated for the Postal Service. The art director was Greg Breeding. [Koslow died in January 2016, so these designs have been "on the shelf" for a while.]