Constant IMMUTABLE_PROPERTIES 

const IMMUTABLE_PROPERTIES: u64 = 0x0B;

Immutable Properties, Property Type 0xB.

Section 11.6: Immutable Properties “contain a sequence of Key-Value-Pairs (see Figure 2) which are also Track or Object Properties”. The Type is odd, so its value is length-prefixed bytes, and those bytes are another delta-typed run starting from 0.