Complex sentence: It debuted atop the Gaon Digital Chart on the chart issue dated July 5--11,2015, and sold 256,390 digital units within its first week of release.
Split into simpler sentences: It debuted atop the Gaon Digital Chart on the chart issue dated July 5--11,2015. It also charted atop the Gaon Download Chart, selling 256,390 digital units within its first week of release.