The FBKLD structure contains information about a bookmark.
ibkf (2 bytes): An unsigned integer that specifies a zero-based index into the PlcfBkfd that is paired with the PlcfBkld containing this FBKLD. The entry that is found at the index specifies the location of the start of the bookmark. Ibkf MUST be unique for all FBKLDs in a given PlcfBkld.
cDepth (2 bytes): An integer that specifies the number of bookmarks in the document of the same type as the bookmark associated with this FBKLD, the ranges of which overlap the limit of the range of this bookmark. To increment the count, a bookmark MUST meet the following constraints:
The FBKLD of the bookmark occupies the PlcfBkld containing this FBKLD.
The limit CP (cpL) and the start CP (cpS) of the bookmark, as specified in the PlcfBkld and the PlcfBkfd it is paired with, satisfy the following in relation to the CP (cpCur) that marks the limit of the bookmark of this FBKLD.