My Backup file 6.7 Gbyte but I have 300+ issue and 20+ knowledge base document

Hi everyone,

 I'm managing a docker Youtrack environment. 

A Emloyee who leaved our company prepared a video playlist to knowladge base for how can we do someting for our environments. 

These videos are taking up 7.0~GB space. When I saw this issue I carried the videos to google drive and add embedded code those articles And I deleted the attachments from knowledge base. But, nowadays, I see again the space taking up is 7.0 GB. 

How can i solve this situation?

Thanks everyone in advance