Complex sentence: The company has experienced substantial growth in the United States where it has 613 stores (April 2011, about 220 more shops than it did in June 2008) and a same-store sales growth rate of 3.9% in Canada and 4.9% in the US.
Split into simpler sentences: The company has experienced substantial growth in the United States, where it has 613 stores (April 2011, about 220 more than it had in June 2008). It has a same-store sales growth rate of 3.9% in Canada and 4.9% in the US.