By default, the pool will adjust the difficulty of your miner automatically over time until you have from 5 to 15 submits per minute. It's a good trade off between bandwidth and accuracy.

You can also set a fixed custom difficulty using the password parameter. For example, if you want to set the difficulty to 1, you would use:

-a kawpow -o stratum+tcp://pool.gaelium.io:3638 -u YOUR_WALLET_ADDRESS -p d=1

Here are the accepted values for the custom diff:

KawPow: from 0.1 to 1024

If the difficulty is set higher than the coin's network difficulty, it will be adjusted automatically.