We calculate the total number of jobs as (int) Math.ceil(processInstanceCount / invocationsPerBatchJob); in a couple of places (e.g. https://github.com/camunda/camunda-bpm-platform/blob/7.10.0/engine/src/main/java/org/camunda/bpm/engine/impl/cmd/ProcessInstanceModificationBatchCmd.java#L103). Math.ceil does nothing here. Should rather do +1 if mod is != 0.
We don't seem to use this value internally for batch processing, so the impact is purely on reporting currently.