Allow me to share some details why you're seeing some discrepancy between the Creditor Summary and Detailed ageing reports.
When comparing two different reports, the variables should be the same. For example, the Report period was set to All Dates on the Detail Report, and the Summary Report was set for Today. The Opening Balance between the two reports will show a different amount.
I've added a screenshot of the comparison between these two reports:
The same scenario goes to other reports if the date was set differently when comparing it to another. To know more details on how to modify the reports, you can check out this article: Customise reports in QuickBooks Online. Also, this includes sub-articles that can be useful in your future task on how to manage and share your customized reports.
I'll be here if you have other questions. You're always welcome to drop a comment below to let me know. Have a great day!