Sign bit, not S bit

rfc9204.md

@@ -992,9 +992,9 @@ positive and the sign bit is set to 0.
 
 The value of Base MUST NOT be negative. Though the protocol might operate
 correctly with a negative base using post-base indexing, it is unnecessary and
-inefficient. An endpoint MUST treat a field block with an S bit of 1 as invalid
-if the value of Required Insert Count is less than or equal to the value of
-Delta Base.
+inefficient. An endpoint MUST treat a field block with a sign bit of 1 as
+invalid if the value of Required Insert Count is less than or equal to the value
+of Delta Base.
 
 An encoder that produces table updates before encoding a field section might set
 Base to the value of Required Insert Count.  In such a case, both the sign bit
@@ -1004,11 +1004,11 @@ A field section that was encoded without references to the dynamic table can use
 any value for the Base; setting Delta Base to zero is one of the most efficient
 encodings.
 
-For example, with a Required Insert Count of 9, a decoder receives an S bit of 1
-and a Delta Base of 2.  This sets the Base to 6 and enables post-base indexing
-for three entries.  In this example, a relative index of 1 refers to the fifth
-entry that was added to the table; a post-base index of 1 refers to the eighth
-entry.
+For example, with a Required Insert Count of 9, a decoder receives a sign bit
+of 1 and a Delta Base of 2.  This sets the Base to 6 and enables post-base
+indexing for three entries.  In this example, a relative index of 1 refers to
+the fifth entry that was added to the table; a post-base index of 1 refers to
+the eighth entry.
 
 
 ### Indexed Field Line