I used * wildcard to clear everything and now wish to check the total number of invalidation requests made. How can I know that?
If you are asking so that you are aware of whether you've crossed the threshold of the free monthly allowance, then may not know that when you send an invalidation request for *(or /*, the leading slash is implied if not provided) then no matter how much content was actually evicted, the number of invalidation requests you made is only 1.
The charge to submit an invalidation path is the same regardless of the number of objects you're invalidating: a single object (
/images/logo.jpg) or all of the objects that are associated with a distribution (/*).— http://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/Invalidation.html
If you are asking how many objects were actually invalidated, that's not a question that actually has an answer. Invalidations are operation that removes all versions of all matching objects from all of the edge caches, if present, but they don't get counted as the process is happening.