Adding on to Shred's answer, VCF is flexible and self-describing so you won't find the meaning of all fields in your VCF in the file specification. See this part of the file spec (linked in your post):
It is strongly encouraged that information lines describing the INFO, FILTER and FORMAT entries used in the body of the VCF file be included in the meta-information section.
so go to the meta-information section. What's that, you ask?
File meta-information is included after the ## string and must be key=value pairs
So you're looking for FORMAT/AQ, FORMAT/AD and FORMAT/RNC. These translate to header (meta-information) lines that look like: