Improve language around verification thresholds.

Co-authored-by: Will Abramson 

Author: msporny

index.html

@@ -4025,10 +4025,10 @@ Group Control
 In the case of group control, the [=DID controllers=] are expected to act
 together in some fashion, such as when using a cryptographic algorithm that
 requires multiple digital signatures ("multi-sig") or a threshold number of
-digital signatures ("m-of-n"). The expression of these additional thresholds for
+digital signatures ("m-of-n"). These additional thresholds for
 verifying a proof can be expressed in a [=verification method=] as described in
 Section [[[#verification-methods]]] or can be an intrinsic part of the
-[=verification method=] where the number of [=DID controllers=] that
+verification material of the [=verification method=], where the number of [=DID controllers=] that
 participated in the generation of a particular digital signature are hidden for
 privacy reasons.
         p>