Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_21938 ( "Round" text, "Main date" text, "Number of fixtures" real, "Clubs" text, "New entries this round" text, "Prize money" text, "Player of the Round" text )

### Question ###
How many categories of new entries this round are there for the fourth round proper?

### Accurate SQL ###

SELECT COUNT("New entries this round") FROM table_21938 WHERE "Round" = 'Fourth Round Proper'