"Under German law, the maximum term for one count of aggravated tax evasion is 10 years. If an accused is convicted of more than one count, the court can increase the maximum to 15 years."
The US is 5 years for each count, half of Germany's.
Macafee was under accused of multiple crimes, which added up to the headline figure of 30 years.
If he had been German it would have 60 years for those same multiple crimes.