LL Cool J performing live at the Staples Center opening for Janet Jackson during her 'Rock Witchu' tour, Los Angeles, California - 17.09.08

The hip-hop star's Exit 13 entered the U.S. Billboard chart last week (beg15Sep08) at number nine.

Simpson's debut country LP, Do You Know, came in at number four and also claimed the top spot on the Top Country Albums chart.

And LL Cool J is said to be baffled by the placings.

A source tells British newspaper the News of the World, "He is stunned. He simply can't believe what's happened."

Source: WENN