Here are the screen shots from the linked web site:
I differ from Richard Connell's statement that superficial letters were usually not used in the Gothic period just to fill in an empty space.
At times when craftsmen like bronze founders could not normally read or write the only way for a learned person to convey a description desired to be appear on a work of art was writing the letters down for the founder to copy.
E.g., a lot of meaningless inscriptions found on medieval sword blades denote that those letters were often not copied exactly and were primarily used as a magic ornamentation. Thus, an additional letter, meaningless though it obviously was, used to fill in an empty space seems quite understandable from the a Late Gothic craftsman's point of view.