[css-color-4][editorial] Clarify Lab a,b range w3c#12208

Author: svgeesus

css-color-4/Overview.bs

@@ -3404,7 +3404,8 @@ Specifying Lab and LCH: the ''lab()'' and ''lch()'' functional notations</h3>
 	These values are signed
 	(allow both positive and negative values)
 	and theoretically unbounded
-	(but in practice do not exceed ±160).
+	(but in practice do not exceed ±160
+	for real-world colors).
 
 	There is an optional fourth <<alpha-value>> component,
 	separated by a slash,