Hello Justus,
In the text is written that
A consolidation of suppliers reduces transport costs by EUR 4 million (EUR 20 million * 20%)
As you may notice, the author talks about a reduction of costs 4M€, It means that, as you were suggesting, the new cosi is: Original cost - Reduction = 20M€ - 4M€= 16 M€.
Does it make sense?
Best,
Luca