Update src/level-ext.adoc

Co-authored-by: Jessica Clarke <jrtc27@jrtc27.com>
Signed-off-by: Tariq Kurd <tariqandlaura@gmail.com>

src/level-ext.adoc

@@ -100,7 +100,7 @@ endif::[]
 |==============================================================================
 
 ^1^ _Mode (<<m_bit>>) can only be set on a tagged capability when {cheri_default_ext_name}
-is supported. Despite being encoded here it is *not* an architectural permission._ +
+is supported, otherwise such encodings are reserved. Despite being encoded here it is *not* an architectural permission._ +
 ^2^ SL isn't applicable in these cases, but this value is reported by <<GCPERM>> to simplify the rules followed by <<ACPERM>> +
 ^3^ These entries are reserved when `LVLBITS=1` and in use when `LVLBITS=2`