Pool settings
The pool is configured to start you mining at 1042 difficulty.
The pool adjusts the per instance difficulty to maintain an average share rate of approximately 3 shares per 10 seconds (18 shares per minute)
However, there is a lower limit set on the difficulty of 42.
If you mine with a username, you can login to the web interface and set a minimum difficulty for mining.
If this value is below the pool calculated value, you'll get the pool calculated value.
If you mine with a BTC address as your username, you can use the cgminer option --suggest-diff to set it for each cgminer.
You can, of course, also use --suggest-diff if you mine to a username.