I'm going through the MS-ONESTORE specification trying to parse a .one
file. The spec states that I ought to find {8DFAB807-A83A-4AC0-
9393-E1DD0691CFB8}
at position 0x10, but instead I find {15AC0EF3-FDFB-4295-9558-7CC34D9F220}
in one note, and {3DE7BDCD-B2DC-4076-9C7A-6BA09C258768}
in another. I cannot find these guids anywhere in the docs. Can someone tell me where I am misinterpreting the spec?
You're looking at a specific example of a file rather than the structure definition. Take a look at the following definition of the structure Header which is linked from the page you referenced.
The specific element at 0x10 appears to be the unique identifier of the specific onenote file, so you'd expect it to be different in every file you parse.