What does it mean if there is a handwritten exit date and a letter next to it on my Thailand entry stamp?

This may be nothing at all but I was just wondering if anyone had any info on my stamp I received at the airport. I was just a little concerned as they seemed to have a good look through my passport and I noticed they wrote my exit date in pen and then there is some kind of letter or initial next to it the only reason I ask I was with 2 other people at the same desk and they all got the normal ink stamp on there date to exit. same as any others in my passport. Just checking its nothing to worry about. Thanks