SNK revealed via their KOF WORLD facebook page that there’s a secret command to unlock a frame counter for inputs. Not only that, but the command has been in the game since release, and no one found it!
Quoted directly from the original post:
Enter the following command in the Main Menu:
, then press X and △ simultaneously.
* Keys: X and △ in the case of a default configuration on PS4.
* For other controllers and configurations, please use the buttons assigned to the “Light Kick” and “Heavy Punch” attacks.
If done correctly, then this is what you see:
Note that this is not frame data for moves, and the two should not be confused. This is a running frame counter between your own inputs.
Source: KOF WORLD