.663 and .163 could be the exact same reaction time depending on the particular track’s timing setup.
On a sportsman tree, each amber (3 of them) lights up exactly .500 seconds apart, on a pro tree, all ambers light up, then green exactly .400 seconds after.
We’ll stick with the sportsman tree, since that’s what most people are used to. Some tracks use the last amber as their base time to start the timer, so a perfect reaction time would be a .500. Most nowadays are starting with .000 to keep things less confusing for n00bs and others.