Suggestions:
- Specify that the Block ID = AB4BA572
- Note that the only known Block Version is 1. Other versions may change the structure of the rest of the record.
- ? Hex offset 48 is a part of the following 7BITSTR and should just be included in the Block Name entry "7BITSTR (offsets 48-57 in hex)". If necessary, you can point out that the first byte of this particular 7BITSTR is the length.
- Count N has hex offsets of 58-5B
- A DWORD is not 8 bits, so it's very confusing for you to say that it is. A bit takes a value of 0 or 1 and a DWORD has 32 bits. However, I don't see the number of bits as useful information, so you should just remove it. The term "DWORD" or even "DWORD (4 bytes)" should be sufficient.

FYI: A half of a byte is called a "nibble", but no one really uses this term. From http://foldoc.org/?nibble
"nibble: Half a byte. Since a byte is nearly always eight bits, a nibble is nearly always four bits (and can therefore be represented by one hex digit)."

- A FLOAT is by definition a single floating point number, so the term "FLOAT (4 bytes / 8 bits)(in Singles)" doesn't seem right. Here are some suggestions: "FLOAT", "FLOAT (4 bytes)", "FLOAT (Single / 4 bytes)".

FYI: A single floating point number is called a FLOAT (or, if necessary, "Single FLOAT") and has 4 bytes. A double floating point number is called a DOUBLE (or, if necessary, "DOUBLE FLOAT) and has 8 bytes.

- I found the following statement a bit confusing: "coordinate dependent on the lot orientation". As far as I know, the only "orientation" that is recognized in SimPE is the Orientation of the lot in the neighborhood, which is not the field that you want. I assume that you're talking about the U11 value, which is not (yet) well documented. Perhaps just "fence coordinate"? We really need to document the U11 value somewhere and how it affects all of the coordinate values in the lot file.
- "GUID ID" is redundant, since a GUID is a type of ID. Use either GUID or ID, but not both.

FYI: GUID is an acronym, meaning a Globally Unique Identifier.

- Can you put each link on a separate line?
- I would rephrase both properties; they are somewhat confusing. How about "Deletable. If deleted, all fence posts on the lot disappear."? The second property is a run-on sentence and needs to be split into several simpler sentences.

Overall, looks good. I hope that you find these suggestions helpful.