I got a spike credit usage at 24 August, it usually only cost at most 3000 credit daily. I don’t know how to trace it down, the top contributing workflows and project workflow overview isn’t helpful.
Currently, the Insights interface is lacking the ability to set an explicit date range and so it does get rather complicated to use it for fact-finding - I’ve described it in-house as a frontend to keep the CxOs happy as it makes things look pretty 
What you should be able to do is drill down by clicking on the entries in the top contributing list. The new screen only really shows the same info, but you can then click on the bar chart for the day you are interested in, but that is about it.
If you are trying to track down credit usage a better place to start is the ‘Plan’/‘Plan Usage’ page as this will allow you to see which project has clocked up credits across all chargeable areas - you can then use the detail shown on the ‘insights’ page to find which day the excess costs happened. Once you know the project(s) and date you then need to look at each run of the project to try and work out what happened from the logs as the only detail provided via the web frontend currently is regarding the time used.
There may be other info recorded, but as I use self-hosted runners, very little detail is logged for the jobs I run.