Error :The query for these buckets is too complex. Remove one or more buckets and retry. Why ? i created 7 buckets with less than 20 items each..why is too complex??

Hi, Bucket has few limitations in the reporting. Few are below 

• Each report can include up to 5 Bucket fields.
• Each Bucket Field can contain up to 20 named groupings. 

https://help.salesforce.com/s/articleView?id=000385482&type=1