diff --git a/css-fonts-5/Overview.bs b/css-fonts-5/Overview.bs
index de0db84755d9..f9dffeedbee7 100644
--- a/css-fonts-5/Overview.bs
+++ b/css-fonts-5/Overview.bs
@@ -149,21 +149,21 @@ the 'ascent-override', 'descent-override', 'line-gap-override', and 'size-adjust
Name: ascent-override
-Value: normal | <>
+Value: [ normal | <> ]{1,2}
For: @font-face
Initial: normal
Name: descent-override
-Value: normal | <>
+Value: [ normal | <> ]{1,2}
For: @font-face
Initial: normal
Name: line-gap-override
-Value: normal | <>
+Value: [ normal | <> ]{1,2}
For: @font-face
Initial: normal
@@ -180,6 +180,11 @@ The 'ascent-override', 'descent-override', and 'line-gap-override' descriptors d
line gap metric of the font, respectively. The `size-adjust`
descriptor defines a scalar by which glyph outlines and metrics from this font are multiplied.
+Both values accepted by 'ascent-override', 'descent-override', and 'line-gap-override' measure
+distance in the block direction. When the text is typeset sideways,
+the first value is used. When the text is typeset upright, the
+second value is used if it is present, and if it isn't present, then the first value is used.
+
When the descriptor value is 'normal', the corresponding metric value is obtained as-if the
descriptor was absent from the @font-face block.
@@ -274,14 +279,14 @@ Issue(5518):
Name: superscript-position-override
- Value: normal | <>
+ Value: [ normal | <> ]{1,2}
For: @font-face
Initial: normal
Name: subscript-position-override
- Value: normal | <>
+ Value: [ normal | <> ]{1,2}
For: @font-face
Initial: normal
@@ -300,7 +305,10 @@ Issue(5518):
Initial: normal
-
+Both values accepted by 'superscript-position-override' and 'subscript-position-override' measure
+distance in the block direction. When the text is typeset sideways,
+the first value is used. When the text is typeset upright, the
+second value is used if it is present, and if it isn't present, then the first value is used.
Font Feature Properties