@Arvind_Mishra , further to what @ChristianHoltfurth said, topics in Solace are fully dynamic - that means a topic can have from 1 to 128 levels.
However, you may have a topic taxonomy. That specifies what levels your topic should conform to. It may be that you have a topic taxonomy that specifies 4 levels. This would be unusual, I think - it’s rather a small number of levels.
You can find out more about topic taxonomies in this blog.