"As part of its plans to implement a stricter legal framework regarding asylum and border controls, the government aims to create between six and 10 closed pre-departure centers and is planning to recruit 400 border guards in the Evros region, 500 new asylum officers on the islands and mainland, as well 800 officers to guard sea borders and the centers."
Greece: New closed centers, 1,700 hirings to improve response to migration challenge (ekathimerini.com, link):
“These pre-departure centers will hold migrants who are slated for deportation until their departure and will hold a minimum of 5,000 and a maximum in some cases of 10,000.”