db_files

I recently tried to add a datafile, and got a message similar to the following:
Cannot create database file, maximum of 30 reached. Then, it went ahead and made the file, although it isn't in the data dictionary.
What's stranger though, is that the db_files is set to 40, not 30, if you do a show
parameter db_files, you get 40. What gives here?

• Dc.