If you have VBO on a simple view (entity listing) with a single filter that have a default value. (the view is filtered by default)

in my case: date filter on date created (with relative default value).

If you empty the default value of this filter, and select all the rows result of the view, only the result with the default filter value are passed to the batch operations.

Means if the views has 500 result with the default filter and 1000 results with the filter empty.
You can select the 1000 rows for an operations but only 500 rows are really passed to the batch operations. (whenever you are in batch page or queue (cron processed) operations .

I test it with the operation "execute an arbitrary PHP code".
I use views 7.x-3.5.