[css-counter-styles-3] Whoops, previous edit was wrong. Just catch the 0-value case directly. w3c#5784

Author: tabatkins

css-counter-styles-3/Overview.bs

@@ -640,13 +640,20 @@ Accumulating Numerals: the ''additive'' system</h4>
 			|S| initially be the empty string,
 			and |symbol list| initially be the list of <a>additive tuples</a>.
 
-		2. If |value| is 0, and there is an <a>additive tuple</a> with a weight of 0, append that tuple's <a>counter symbol</a> to |S| and return |S|.
+		2. If |value| is zero:
+
+			1. If |symbol list| contains a tuple with a weight of zero,
+				append that tuple's <a>counter symbol</a> to |S| and return |S|.
+
+			2. Otherwise, the given counter value cannot be represented by this counter style,
+				and must instead be represented by the fallback counter style.
 
 		3. For each |tuple| in |symbol list|:
 
 			1. Let |symbol| and |weight| be |tuple|'s [=counter symbol=] and weight, respectively.
 
-			2. If |weight| is zero, [=iteration/continue=].
+			2. If |weight| is zero, or |weight| is greater than |value|,
+				[=iteration/continue=].
 
 			3. Let |reps| be <code>floor( |value| / |weight| )</code>.
 
@@ -658,7 +665,8 @@ Accumulating Numerals: the ''additive'' system</h4>
 
 		4. Assertion: |value| is still non-zero.
 
-			The given counter value cannot be represented by this counter style, and must instead be represented by the fallback counter style.
+			The given counter value cannot be represented by this counter style,
+			and must instead be represented by the fallback counter style.
 	</div>
 
 	Note: All of the predefined additive ''@counter-style'' rules in this specification