For some batch operations, it appears that there is a miscount on both the output when running by drush or seeing the completed status in the Batch operation UI
Processed item_11. [85%] [12/14]
Processed item_12. [92%] [13/14]
Process completed: Tried 14 out of 14 cron strings. See the log for debug and manual validation.
The item count says 12 but starts at 0 so it means 13. However the totals reported say 14. So it looks like a difference of 2 but is really only off by 1.
However others, the count is correct. Something seems flimsy here. Ought to adjust the item output to not start at 0 as well. It leads to confusion.
Fixed
1.0
User interface
This was caused if an array of items to process has an index of 0. I altered to make sure anything with an index of 0 gets rekeyed to start at 1.