Complex sentence: In 2008, the group topped "Billboard" magazine's list of the all time most successful "Hot 100" artists; as of 2013, they hold the record for most number-one hits on the Hot 100 chart with 20.
Split into simpler sentences: In 2008, the group topped "Billboard" magazine's list of the all time most successful "Hot 100" artists. As of 2013, they hold the record for most number-one hits on the Hot 100 chart with 20.