Icloud backup was successful but icloud storage not increase

Im using iphone 7plus 128gb and also purchase icloud storage 200gb, the problem is my iphone storage already full then i do the icloud backup and it was written last successful backup but the icloud storage only 1.5gb, how to make sure that icloud backup is really successful and all the data safely stored to the icloud storage? because i want to reset all the content and setting to reduce my iphone storage back