What is the "second round" exactly?
Syriza abolished the system which gives a 50 seat winners bonus but as they do not have a supermajority the changes can only be implemented in the second next election. When ND replaced Syriza they changed the system again so that the largest party gets a 20 seats winners bonus along with a sliding bonus for parties above >25% of the vote. As they too do not have a 2/3rd majority their system will only be used after the next election.
No party will likely win a majority on its own under Syriza's fully proportional electoral system and as no one seems interested in trying to build a majority coalition it is very likely that there will be another election soon under the ND electoral system with a smaller winners bonus and seat bonuses for larger parties. This is the "second round".