No, the size you see in the list is the sum of all layers in the image. The layers can be shared between images, so this number never reflects the actual size on your disk.
You should first find the images that are not related to others with
docker image ls -f 'dangling=true'
These are the images you can delete. To delete them all at once (if you are really sure about that) run
docker image rm $(docker image ls -f 'dangling=true' -q)