-The SETBID record indicates which block ID is being described. The standard
-DEFINE_ABBREV record specifies an abbreviation. The abbreviation is associated
-with the record ID, and any records with matching ID automatically get the
-abbreviation.
+The SETBID record indicates which block ID is being described. SETBID
+records can occur multiple times throughout the block to change which
+block ID is being described. There must be a SETBID record prior to
+any other records.
+</p>
+
+<p>
+Standard DEFINE_ABBREV records can occur inside BLOCKINFO blocks, but unlike
+their occurrence in normal blocks, the abbreviation is defined for blocks
+matching the block ID we are describing, <i>not</i> the BLOCKINFO block itself.
+The abbreviations defined in BLOCKINFO blocks receive abbreviation ids
+as described in <a href="#DEFINE_ABBREV">DEFINE_ABBREV</a>.
+</p>
+
+<p>
+Note that although the data in BLOCKINFO blocks is described as "metadata," the
+abbreviations they contain are essential for parsing records from the
+corresponding blocks. It is not safe to skip them.