Edited Saved as fullsizeoutput_9e7a.jepeg and not given option to save original file

I am new to Photoshop on Mac. I have edited a number of photos and half the photos are saved back into their original site with the update (ie, IMG_4809.jpeg) and half are saved as fullsizeoutput_9e7a.jpeg. and does not go back to the original file. I do not know how to change this so the files are only saved back to the original file but updated. I set my preferences to do this but the fullsizeoutput destination file persists. Can anyone help me?