[css-step-sizing] Add notes/issues from review mtg in Tokyo

Author: kojiishi

css-step-sizing/Overview.bs

@@ -95,12 +95,16 @@ Values have the following meanings:
 
 Issue: Naming under discussion.
 
+Issue: Should the step baseline position be percent?
+Not much precision is needed, but
+there was one feedback that percent is easier to use.
+
 Stepping Line Box Heights {#height}
 -----------------------------------
 
 When the <a>step unit</a> is set to a positive <<length>>,
 the line box heights are rounded <i>up</i> to
-the closest multiple of the unit.
+the multiple of the unit.
 
 [[!CSS21]] <a href="https://drafts.csswg.org/css2/visudet.html#line-height">&#xA7;10.8 Line height calculations</a>
 defines how to compute the line box height
@@ -118,6 +122,7 @@ The <a>step baseline position</a> determines
 how the additional spaces are distributed.
 
 * When it is not set,
+    the height is rounded up to the closest multiple of the <a>step unit</a>, and
     the space is distributed to
     <a>over</a>-side (T) and <a>under</a>-side (B) equally,
     so that the original line box appears at the center of the
@@ -176,6 +181,13 @@ how the additional spaces are distributed.
   </pre>
 </div>
 
+<div class="note">
+It is usually recommended to set the 'line-height' lower than
+the <a>step unit</a>.
+The used line height can increase due to several factors such as
+the use of 'vertical-align' or font fallback.
+</div>
+
 Aligning Baselines {#baseline}
 ------------------------------
 
@@ -281,7 +293,7 @@ Non-negative <<length>>s are valid.
 
 When this property is set to a positive <<length>>
 and the <a>available inline size</a> is <a>definite</a>,
-the <a>available inline size</a> is rounded <em>down</em>
+the <a>available inline size</a> of the element is rounded <em>down</em>
 to the closest multiple of the specified <<length>>
 before it is used.
 
@@ -292,6 +304,21 @@ are the multiple of the specified <<length>>
 if there were other constraints.
 </div>
 
+When this property is applied to a multi-column element,
+the <a>available inline size</a> of the content box is not rounded but
+the <a>available inline size</a> of the <a>column box</a> is rounded.
+
+<div class="note">
+When using this property with CSS layout features such as tables or flexbox,
+authors are expected to apply this property to
+item boxes rather than container boxes;
+e.g., table cells rather than tables, or
+flex-items rather than flex-containers.
+
+However, the special case above is needed because
+authors cannot style <a>column boxes</a>.
+</div>
+
 <div class="example">
   This property improves the justification
   for Han ideograph-based scripts such as Chinese or Japanese.