Original sentence: It extends roughly 290 km (180 mi) eastwards from the lower Vistula River to the Poland-Lithuania border and occupies an area of roughly 52,000 km² (20,000 sq mi)
Edited sentence: It extends roughly 290 km (180 mi) eastwards from the lower Vistula River to the Poland-Lithuania border and occupies an area of roughly 52,000 km² (20,000 sq mi)