== implicit mode, concurrency 4, 24 records on one topic partition
records handled = 24
distinct listener threads that handled records = 2
  implicit-C-1
  implicit-C-2
== manual mode (ShareAckMode.MANUAL), listener takes a ShareAcknowledgment
again delivery #1 -> release
again delivery #2 -> acknowledge
bad delivery #1 -> reject
ok delivery #1 -> acknowledge
