[css-color-4] Add example of specified out of range alpha, both with and without calc #8318

Author: svgeesus

css-color-4/Overview.bs

@@ -5620,6 +5620,20 @@ Serializing alpha values</h3>
 		</p>
 	</div>
 
+	Because <<alpha-value>>s which were specified outside the valid range
+	are clamped at parse time, the specified value will be clamped.
+	However, per [[css-values-4#calc-range]], <<alpha-value>>s
+	specified using calc() are not clamped when the specified form is serialized;
+	but the computed values are clamped.
+
+	<div class="example" id="ex-alpha-clamp">
+		<p>For example an alpha value which was specified directly as 120%
+			would be serialized as the string "1".
+			However, if it was specified as calc(2*60%)
+			the specified value would be serialized as the string "calc(1.2)".
+		</p>
+	</div>
+
 
 <h3 id="serializing-sRGB-values">
 Serializing sRGB values</h3>
@@ -5767,6 +5781,8 @@ Serializing sRGB values</h3>
 	and not the string "rgb(218.000, 165.000, 32.000)"</p>
 </div>
 
+
+
 <h3 id="serializing-lab-lch">
 Serializing Lab and LCH values</h3>