# Pastebin yWwsMPrc
1. "next section" -> "section 13.1.1 Interpolation of <filter-function>s"
2. what does "each possible <filter-function> pair" mean? "Each <filter-function> for which there is a corresponding item in each list"?
3. Instead of "Add the missing equivalent <filter-function>s from the longer list to the shorter list" I think you need to make it clear that the new functions get appended to the shorter list (i.e. to the end of the list).
4. Minor point: 13.1.1 Starts off like a list of instructions "the steps ... must be run" but then each item is a description "Interpolated as length." If they're instructions, then it should probably be "Interpolate as length".
5. "Given two filter values Va and Vb, returns the concatenated lists of the two filters." This should probably mention the order and the fact that they are space separated? e.g. "Va Vb". Also, without referencing Web Animations I'm not sure that using Va and Vb makes much sense. It might be better to say, "Given two filter values representing an base value (<var>base filter list</var>) and a value to add (<var>added filter list</var>), returns the concatenation of the the two lists: &lsquo;<var>base filter list</var> <var>added filter list</var>&rsquo;.
6. The example looks good, although technically you only need additive="sum" on the second <animate>