What is a Canon created .afg file?

I have been shooting with my current body for a long time. It is 5 generations old now and beyond time for an upgrade. I have shot over 100,000 frames with it. Needless to say I hope it holds out until I can afford the body I want to replace it with.

On May 31st I had a family session and the shoot went as planned and all the images recorded to the card like they always have. There is one exception though. A file type .afg appeared, and only one of them. The camera wrote the file to the card when I was shooting. Of course at the time I knew nothing about it. I noticed it in post.

Here is a screen grab of the files from the card. If anyone has any idea what a .afg and how the camera recorded it to the card that would be great.