It's/that's not saying much, etc. American British informal
Used to indicate that it is not unexpected that one person or thing is superior to another since the other person or thing is so terrible
Jane is more excellent at processing the machine than Peter, but that’s not saying much because Peter is a newbie.
She plays badminton better than I do but that's not saying much.
Jane's idea of the marketing campaign contributed greatly to a product's sales figures, but it isn't saying much if we consider how other members devoted to it.
It was often said by a photographer when he would like small children to look at the camera and smile before he took a photo.
When the photographer said “watch the birdie”, all of us looked at the camera and smiled.