Parsing EBML Void element?

Question

C++ / C#

Good afternoon, I want to warn you that I am faced with such tasks for the first time, therefore I can ask obvious things for someone, please do not kick me for this. I decided to parse the webm file, namely to check and get the Void element, I found an example on the github ( https://gist.github.com/mganeko/9ceee931ac5dde298e81 ) but as it turned out it does not work. I decided to find and fix the error, I figured out the code and the algorithm itself, but apparently I'm missing some detail from the specification ( https://matroska.org/technical/specs/index.html) , the problem is that this code shows that absolutely in all the same Void element with the same value , but for example (EBML Inspect) says something else. According to the algorithm, after finding 2 top-level elements (EBML and Segment), it works correctly here, the buffer pointer finds the [EC] byte (as it is written in the specification), but then it takes the adjacent byte (0x86) and, according to the same specification, its dimension is 1 byte and exits, but in fact the data 0xEC comes just after this byte (86) another 5 bytes (for example, in EBML Inspect it shows 39 33 34 39 35 39 ). So the question is what am I missing?
PS Added the C++ tag because I think they come across this kind of work more often in their day to day work.