For a sailing vessel under power...this is the combination of lights required. Note that the "masthead light" which may be placed on the front of the mast OR the top of the mast has an arc of 225 degrees.
If your boat has a proper "masthead light" at the top of the mast...it cannot be used for anchoring as it is not an all around white light. You can use a Davis anchor light ALONE when you are at anchor.
Conversely...if your "masthead light" is NOT a 225 degree light...but rather an all around light...it is really an anchor light and you need a "steaming light" lower on the mast. Given the preinstalled wiring...I would doubt this.