Original: The dark, elliptically-shaped spot (with initial dimensions of 13,000 × 6,600 km, or 8,100 × 4,100 mi) was about the same size as Earth, and was similar in general appearance to Jupiter's Great Red Spot.
Simplified: The dark, elliptically-shaped spot (with initial dimensions of 13,000 × 6,600 km, or 8,100 × 4,100 mi) was about the same size as Earth, and was similar looking to Jupiter's Great Red Spot.