The timerange you apply on the search works based on the field "_time" which denotes when the event occurred.
In your results, the dates you see are different timestamp field and not _time. Those timestamp fields (dv_work_start dv_work_end) may not be related to the _time field (they're not per your data), hence you see variety of dates.
I would suggest to check the timestamp parsing of your sourcetype to see what time is being considered as time. If possible update your sourcetype to use one of `dv_work*` field so that you can filter based on that.