The problem is you are conflating sentences and time served. Seven years is (or was, haven't kept up with it in a few decades) was the minimum for a life sentence. So the press can get a headline 'killer sentenced to life for murder', but the parole board determines the amount of time served.
And even there, your statement needs some qualifications. The guys getting out after 7 years generally had clean records before going in (and are generally well behaved in prison), and killed a wife or girlfriend who knew how to push their buttons. Someone with priors or with a cold blooded plot or excessive brutality was going to do more.
I think it's OCGA 42-9-45. And they used to have paper worksheets that defense lawyers could go through with their clients when discussing plea deals. It's probably all computerized these days.
Found this online - can't vouch for its accuracy
https://kleinrock-law.com/apps/parole/parole.html
Nope you completely missed my point. Yes I said time served. On a 25 year sentence parole eligibility may be as early as 1/3 time served but is more common at 1/2 time served. That at best would be 8 years 4 months for beating a dog vs 7 years for killing someone. Still an absurd, cruel and unusual punishment for beating a dog.