I am attempting to parse a SWF file and I believe I may have found an error on page 135-6 of the "SWF File Format Specification Version 10" (http://www.adobe.com/devnet/swf/pdf/swf_file_format_spec_v10.pdf). This is where the STYLECHANGERECORD is defined. The spec references two fields, FillBits and LineBits that are used to define the lengths of unsigned bit strings read from the SWF file; however, these fields themselves are not defined in the STYLECHANGERECORD.
I have a similar issue with the nGlyphs field used as an array length by DEFINEFONT; The nGlyphs field is never defined itself in that record.
I tried using Adobe's general contact form as well as contacting firstname.lastname@example.org as they say to do on the spec download page; however, I haven't heard back. I hope one of you who are reading this might have some insight to either the completeness of the spec, or what I am misunderstanding.
I know this post is extremely old, but it'd be good to have the answer here for posterity. I ran into the same confusion.
Apart from DefineShape2 and DefineShape3 shapes, FillBits and LineBits are fixed throughout a single shape (presumably because the length of the linestyle and fillstyle arrays are fixed throughout a single shape). They're defined at the beginning of the SHAPE structure (on page 133 of the v10 format spec).