To remove an anchor, first lightly score around the anchor to reduce contact with the deck.
Then, drill and tap the center hole with a 5/16-18 tap. The drill bit and tap comes as a set. Drill bit size 17/64".
Then place a metal tube over the anchor. A 3/4" copper coupling should fit the scored area around the anchor.
Then, screw in a long 5/16-18 bolt with 2 big washers and a coupling nut above the washers. The bolt will need to be about 6 to 8 inches long to accommodate the anchor, coupling and coupling nut.
Then, hold the bolt and tighten the coupling nut to pull the anchor.
Scoring around the anchor a little bit and having the copper coupling sit in the scored area should reduce the risk of surface damage, but pulling an anchor always risks damaging the deck.
If you use a 3/4" hole saw to drill the top part of the anchor, that will remove the ridges around the top of the anchor, which will reduce the risk of surface damage.
To keep the hole saw steady without wobbling, you can first drill a hole in a piece of wood and then put that hole over the anchor then drill through the hole.
The hole for the anchor is 3/4", but the top ridges are slightly larger. So, when the anchor is hammered in, the ridges dig in and get compressed, which holds the anchor in place.
Note: It looks like the screws were cut off. Probably because the anchors were stuck up and the service person didn't want to leave them due to safety concerns.
