The circle of twelve gold stars on a blue field (adopted 1955 by Council of Europe, 1986 by EC) symbolizes unity, solidarity, and harmony — not a count of nations.
Arsène Heitz (designer) and Paul M. G. Lévy (Council of Europe) both confirmed: the number is fixed and does not change with enlargement. The EU has 27 members (2024); the flag still has 12 stars.
Circle = unity. Blue = Western sky/peace. Gold = enlightenment. Twelve = perfection/wholeness. Zero = number of members represented.