I don't have exact value to tell you as this is handled internally by pega engine.
But you should not be concerned about it.
Below are few details I found out, it may give you better idea
Once loaded into the ConclusionCache, individual conclusions stay there until they are either invalidated (due to a rule or data change) or they age out due to disuse. Conclusions are kept in a list ordered by their last use timestamp. As the conclusion cache is used, it occassionally checks the least-recently-used conclusion to see if it has passed its "pruning age"
For the count it depends on various entries as listed below