Complex sentence: Throughout the war, "Mărăști" carried out a total of 28 escort missions, "Mărășești" 21, plus 6 joint missions for a grand total of 55 escort missions.
Split into simpler sentences: Throughout the war, "Mărăști" carried out a total of 28 escort missions and "Mărășești" 21. There were 6 escort missions in which both cruisers took part, resulting in a grand total of 55 escort missions.