These are Unix Timestamps in milliseconds.
Search for the file in your device's "Downloads" or "DCIM" folders. Nwdn File Temp 1608701398696 Mh1608701496834 jpg
This prefix is sometimes used by browser extensions like TwitterMediaHarvest or similar social media scrapers to tag files they have processed. jpg: The standard extension for a JPEG image. Origin and Context These are Unix Timestamps in milliseconds