42 cents is accurate for stockholder purposes. The IPO closed 04/13/2011 so they didn't include the portion of the earnings from the company in this quarter's EPS for the 42 cents. If you include that portion of the quarter's earnings then it's 52 cents.
From the filing "Net income for the abbreviated time frame between closing of the CVR Partners initial public offering (IPO) on April 13, 2011, to the end of the second quarter 2011 was $30.8 million, or 42 cents per common unit."
"Reflective of net income per common unit since closing the Partnership’s initial public offering (“Offering”) on April 13, 2011. The Partnership has omitted net income per unit for the periods in 2010 because the Partnership operated under a different capital structure prior to the closing of the Offering and, as a result, the per unit data would not be meaningful to investors. Based upon the full quarter’s net income, net income per common unit would have been $0.52 per common unit."