I'm not sure I understand the question; I think you're confused about what a "chunked response" is.
A HTTP Chunked Response (see RFC2616) does not contain a Content-Length response header; it instead sends the response body in multiple blocks, each preceded by a chunk length value in Hex. To see an example of this, simply click any plaintext HTTP response in Fiddler that has a body, click the Inspectors tab, click the Transformer response inspector, and check the Chunked Transfer Encoding box at the top. Then click over to the Raw inspector and see what happened to the body.
In contrast, a HTTP/206 response is a partial response that only contains a portion of the response body. These responses are sent when the client sends a Range header indicating which portion of the response it wants; these ranged-requests are usually sent when the client already has part of a file locally and wants to retrieve the rest of it. The response body doesn't have any special format; only the Content-Range header tells the client which portion of the response was returned.