The A1559 Sponge used in the FH-800 Iron holder that comes with the HAKKO FX-888D Soldering Station, is a compressed material that is die-cut from a large sheet of material. This die cutting scores two semi-circular areas of the sponge material that are adjacent to the elongated openings in the sponge.
When you install a new sponge, it is best to dampen the sponge with de-ionized or distilled water and squeeze out any excess water. Then, remove the two semi-circular areas of the sponge and place them in the bottom of the sponge tray of the iron holder. These small pieces of sponge will absorb water from the bottom of the sponge tray and will aid in keeping the main sponge damp through capillary action.
The drawing that you see in the user manual shows the sponge AFTER the semi-circular areas have been removed and installed in the iron holder, while the online picture of the sponge shows the sponge after it has expanded from contact with water and WITH the semi-circular areas still attached.