Don't remove anything from any marker rocks. Whatever is covering the rock, being it algae, moss, lichen, will be used as a medium to make shapes and symbols that are seen best from a little ways back. The best things are eyes that are made from lichen to go along with animal heads or faces. Sometimes they are very intricate. Sometimes it just white patches that were meant to get your attention or make something stand out. But your V is likely just telling you it's a just marker that is being used in combination with other nearby ones. Like a triangle, line, geometric pattern etc. You can't really often get any more info from it, it's just a marker. Find the other nearby boulders and map them out and see if something makes sense out it.
Also most of these weren't meant to look like tooled "carvings". It just wasn't done this way. When you walk up close to a marker that makes an image it is supposed to look natural and not man made. That is part of the illusion on all of these locations. Any "tooled" looking type carvings I would take as something to confuse you or something heavily coded that you won't likely figure out.
