Peer Object Cache Metrics

At the Peer metrics callback, I get :ObjectCache metrics like {:lo 0, :hi 1, :sum 3996966, :count 4007439}. According to the documentation, I assume that I can calculate the hit ratio with (/ (double sum) count). My problem is that the hit ratio is always very near to one even if I have considerable :StorageGetBytes. Do I have a false understanding of the :ObjectCache peer metric? I use Datomic Pro v0.9.5966.