DB2 - Why new multiple C000000x subfolders are created in Archive Log folder?
This is completely normal.  Each of these directories are for each unique log chain.  If you are familiar with software version control, each log chain is like a branch.

A new log chain is created each time you restore a database and roll forward to a point in time other than end of logs.  

Here is why:  You have a database, SAMPLE.  It has reached the log file S007500.LOG.

If you restore the database back to the point in time that corresponds to the log file S007000.LOG, what should DB2 do with the fact that you now have 2 sets of log files with the names S007001.LOG ... S007500.LOG?  They represent 2 unique sets of transactions, and they are called log chains.

So, when you create a database, DB2 creates the first log chain, C0000001.  If you restore the database, it creates C0000002, etc.

By preserving these log chains, DB2 gives you the ability to restore each unique series of transactions for a database.