[css-color-hdr] clarify serialization is the same

Author: svgeesus

css-color-hdr/Overview.bs

@@ -101,7 +101,10 @@ Predefined colorspaces for HDR: {#predefined-HDR}
 =====================
 
 	In addition to the <a href="https://drafts.csswg.org/css-color-4/#predefined">SDR
-	colorspaces</a> defined by CSS Color 4, the following HDR colorspaces are defined:
+	colorspaces</a> defined by CSS Color 4, the following HDR colorspaces are defined
+	for use in the color function [[css-color-4#color-function]].
+
+	Serialization of values in these new colorspaces is identical to the decription in [[css-color-4/#serializing-color-values]].
 
 <dfn export>rec2100-pq</dfn> {#valdef-color-rec2100-pq}
 ---------------------------
@@ -120,9 +123,8 @@ Predefined colorspaces for HDR: {#predefined-HDR}
 	(IEEE standard 754-2008.)
 	from BT.2100 pp. 9-10? (or any wider representation, like float or double)?
 
-	Issue: should the range be in absolute nits, ie [0.0, 10,000]? Probably not.
-
 	Issue: should the values accept % as well as number? so 19% as well as 0.19.
+	Probably yes.
 
 	The Perceptual Quantizer (PQ) electro-optical transfer function is used
 	[[SMPTE-ST-2084]],[[!Rec_BT.2100]].