I’m assuming it’s because of this, which is actually a series made in 1993. Regardless, it should probably be changed because it’s going to bother me every time I see him now.
The number in parentheses refers to the date of the first issue of the series listed. In Carnage’s case, “Amazing Spiderman.”
https://forums.505go.com/discussion/30336
quick search, this was asked and answered in his character thread. Enjoy!