MergeContent creates bins too early when a lot of data is queued up

I have a MergeContent Processor with Min Entries = 10, Max Entries = 10. No timeout. Default of 5 buckets. If I queue up 56 flowfiles, I should get 5 merged flowfiles and have 6 remaining in the queue. Instead, I get 6 merged flowfiles, with the last one having only 6 entries.