[css-values-4] Copy over bracket range definition

These changes were added to Level 3 in
8ea8d7d
and
1265976

(And fix a tabs-vs-spaces error that bikeshed was choking on.)

css-values-4/Overview.bs

@@ -84,6 +84,9 @@ Component value types</h3>
 		<li>
 			basic data types, which appear between <css>&lt;</css> and <css>></css>
 			(e.g., <<length>>, <<percentage>>, etc.).
+			For <a>numeric data types</a>,
+			this type notation can annotate any range restrictions
+			using the [[#numeric-ranges|bracketed range notation]] described below.
 
 		<li>
 			types that have the same range of values as a property bearing the same name
@@ -782,14 +785,42 @@ Numeric Data Types</h2>
 	they represent the value’s abstract quantity,
 	not its syntactic representation.
 
-		Properties may restrict numeric values to some range.
-		If the value is outside the allowed range,
-		unless otherwise specified,
-		the declaration is invalid and must be <a href="https://www.w3.org/TR/CSS21/conform.html#ignore">ignored</a>.
 
-		CSS theoretically supports infinite precision and infinite ranges for all value types;
-		however in reality implementations have finite capacity.
-		UAs should support reasonably useful ranges and precisions.
+<h3 id="numeric-ranges">
+Range Restrictions and Range Definition Notation</h3>
+
+	Properties can restrict numeric values to some range.
+	If the value is outside the allowed range,
+	then unless otherwise specified,
+	the declaration is invalid and must be <a href="https://www.w3.org/TR/CSS21/conform.html#ignore">ignored</a>.
+	Range restrictions can be annotated in the numeric type notation
+	using <dfn>bracketed range notation</dfn>,
+	<code>[<var>min</var>,<var>max</var>]</code>
+	within the angle brackets, after the identifying keyword,
+	indicating a closed range
+	between (and including) <var>min</var> and <var>max</var>.
+	For example, <<integer [0,10]>> indicates an integer between 0 and 10, inclusive.
+
+	Note: CSS values generally do not allow open ranges;
+	thus only square-bracket notation is used.
+
+	CSS theoretically supports infinite precision and infinite ranges for all value types;
+	however in reality implementations have finite capacity.
+	UAs should support reasonably useful ranges and precisions.
+	Range extremes that are ideally unlimited
+	are indicated using &infin; or &minus;&infin; as appropriate.
+	For example, <<length [0, &infin;]>> indicates a non-negative length.
+
+	If no range is indicated,
+	either by using the <a>bracketed range notation</a>
+	or in the property description,
+	then <code>[&minus;&infin;,&infin;]</code> is assumed.
+
+	Note: At the time of writing,
+	the <a>bracketed range notation</a> is new;
+	thus in most CSS specifications
+	any range limitations are described only in prose.
+	This does not make them any less binding.
 <!--
 		The recommended minimum ranges and precision,
 		and the required rounding and clamping rules,
@@ -3248,7 +3279,7 @@ Serialization</h3>
 			2. The percentage, if present
 			3. The dimensions, ordered by their units <a>ASCII case-insensitive</a> alphabetically
 			4. <a href="#comp-func">Comparison</a>, <a href="#trig-funcs">trigonometric</a>
-			  and <a href="#exponent-funcs">exponential</a> functions,
+				and <a href="#exponent-funcs">exponential</a> functions,
 				in the order they appeared in the original expression.
 
 		2. Serialize all the terms,