Nos99 is right. 15 frames on the dot.
Now you know you react to stimulus in 15 frames. Practice punishing moves slightly slower than 15 frames on reaction (You may need a partner for this) and figure out just how much time you need to identify moves. You suddenly know which moves you need to fear, and which moves you don’t. You know what options are available to you, and which ones are well-beyond your reach.
You react slightly faster than I do, according to that gizmo, but I can still do shit like DP EX Chicken Wing at a distance, or Abel’s Medium Wheel Kick. So my effective “reaction to input” time is about 22 to 24 frames, and this is online. Now that I know that, I can pretty readily identify what I need to do to shut down my opponent’s options, and whether or not I need to be wary of some of the faster ones.