When erosion is used then every node that is adjacent to an obstacle will get the tag first tag. Every node 2 nodes from an obstacle will get the tag first tag + 1. Every node 3 nodes from an obstacle will get the tag first tag + 2 and so on until it gets to the tag first tag + erosion iterations. The nodes which are further away from obstacles will still have the Basic Ground tag.
In your example first first tag = 3 and erosion iterations = 1 then all nodes which are exactly 1 node from an obstacle will get tag 3 and all other nodes will get tag Basic Ground (0).
Keep in mind that you can show an overlay of the tags in the scene view if you set the ‘Graph Coloring’ mode to ‘Tags’. To see the tags more clearly you may want to enable ‘Show Surface’ in the grid graph settings.
If your goal is to prevent a unit from going too close to the walls, then you should disable the first few erosion tags, but keep the Basic Ground tag.
