Brokers said the shipowner will take delivery of the 2,340-teu vessels in 2016.
It already has eight sisterships being built at Yangfan, which were ordered in 2012 and 2013.
TradeWinds reported at the time that the whole 12-ship series could be worth $318m, with the units priced at $26.5m each.
Schulte and compatriot Peter Dohle signed finance deals worth $1.2bn with Export-Import Bank of China (China Exim Bank) earlier this year, with the money earmarked for new ships.
