When caching is enabled on the WindowStoreBuilder, it creates a CachingWindowStore. However, it incorrectly passes storeSupplier.segments() (the number of segments) to the segmentInterval argument.
The impact is low, since any valid number of segments is also a valid segment size, but it likely results in much smaller segments than intended. For example, the segments may be sized 3ms instead of 60,000ms.
Ideally the WindowBytesStoreSupplier interface would allow suppliers to advertise their segment size instead of segment count. I plan to create a KIP to propose this.