[css-values-5] Mark progress() as a math function, call out the other *-progress() functions as *not* math functions.

Author: tabatkins

css-values-5/Overview.bs

@@ -566,6 +566,7 @@ Calculated Progress Values: the ''progress()'' notation</h3>
 	between two other [=calculations=]
 	(the [=progress start value=]
 	and [=progress end value=]).
+	''progress()'' is a [=math function=].
 
 	The syntax of ''progress()'' is defined as follows:
 
@@ -589,7 +590,8 @@ Calculated Progress Values: the ''progress()'' notation</h3>
 	or do enough places auto-convert that it's not necessary?
 
 	Note: The ''progress()'' function is essentially syntactic sugar
-	for a particular pattern of ''calc()'' notations.
+	for a particular pattern of ''calc()'' notations,
+	so it's a [=math function=].
 
 <h3 id="media-progress-func">
 Media Query Progress Values: the ''media-progress()'' notation</h3>
@@ -624,6 +626,9 @@ Media Query Progress Values: the ''media-progress()'' notation</h3>
 	The result will be a <<number>>,
 	determined by [=calculating a progress function=].
 
+	Note: ''media-progress()'' is <em>not</em> a [=math function=];
+	it's just a function that evaluates to a <<number>>.
+
 <h3 id="container-progress-func">
 Container Query Progress Values: the ''container-progress()'' notation</h3>
 
@@ -660,6 +665,9 @@ Container Query Progress Values: the ''container-progress()'' notation</h3>
 	''container-progress()'' resolves its <<size-feature>> query
 	against the [=small viewport size=].
 
+	Note: ''media-progress()'' is <em>not</em> a [=math function=];
+	it's just a function that evaluates to a <<number>>.
+
 
 <!-- Big Text: *-mix()