What are things that are less than 1KG pictures?

Less than 1KG picture may refer to a photograph that has been taken of an item that weighs less than 1 kilograms. But I think in this case the measure means how large the image is: it must not measure 1000 gigabytes ( 1 kilo = 1000) but that would be so large an image I do not understand why to limit such a large maximum value. Are you sure it was 1KG and not 1KB or GB? 1KB = one kilobyte would be 1000 bytes. 1GB=gigabyte would be quite large too