Complex sentence: Currently TG4's top ten programmes range from 40,000 to 100,000 viewers, but their top show can be has high as 250,000; like other television services they achieve their highest viewing figures with sporting events.
Split into simpler sentences: Currently TG4's top ten programmes have ranged from 40,000 to 100,000 viewers, but their top shows have reached as high as 250,000. Like other television services TG4 achieves their highest viewing figures with sporting events.