Two small animated semi-circular arrows appear after updating a field by script. ??

Two small animated semi-circular arrows appear after updating a field by script. ??

If I check user input (On User input), format it, and then write the formatted data back to the same field, two small animated semi-circular arrows appear to the right of the field and the field contents persist into the next record.
 
I can't find any reference to this in the documentation.  Can anyone help/explain?