That's a world record sized cat then general...
The largest cat on record weighed 48'ish pounds...
The cat in your photo, even after gutting, is just not even near the 50 pound range unless it was eating dumbells...grin...
The lion in the below picture with my brother in it only weighed 52 pounds for reference.
I'm not trying to rain on your parade one bit nor call your integrity into question. I've been around many, many cats.
I would guess your scale is malfunctioning...
Are you going to mount the cat?