One human year doesn’t exactly equal to seven dog years.
The first year for a dog is devoted to growth, physical, sexual, and everything else.
During that first year, a dog goes through the equivalent of babyhood, early childhood, adolescence, puberty, and the late teens.
When it begins its second year the dog is already a young adult.
You can count a dog’s first year as being the equivalent of 20 human years, then figure that every additional year equals about 4 human years.