Graylog Shows Various Unprocess Message Count

Why does graylog show the following:
The journal contains 8,698,975 unprocessed messages in 48 segments, 192 messages appended
And then about three seconds later, show:
The journal contains 17,948,386 unprocessed messages in 52 segments, 644 messages appended
Then about three seconds later, shows unprocessed cound similiar to the original message:

Most likely because it’s unable to connect to Elastiscearch:

Check the logs of your Graylog node(s) for details about the error.