font-size: 16px

https://ypen.gov.gr/

https://www.dei.gr/el/gia-to-spiti/ypostiriksi-epikoinonia/apantiseis-gia-tin-energeia/dei

You can see how this popup was set up in our step-by-step guide: https://wppopupmaker.com/guides/auto-opening-announcement-popups/