Update index.bs

Co-authored-by: Julian Descottes <[email protected]>

index.bs

@@ -9788,7 +9788,7 @@ The [=remote end steps=] given |session| and |command parameters| are:
 1. Let |arguments| be the <code>arguments</code> field of |command
    parameters| if present, or an empty [=/list=] otherwise.
 
-1. Let |user contexts| be [=set/create=] with |command parameters|[<code>userContexts</code>]
+1. Let |user contexts| be [=set/create|create a set=] with |command parameters|[<code>userContexts</code>]
    if |command parameters| [=map/contains=] [<code>userContexts</code>] and an empty [=/set=] otherwise.
 
 1. For each |user context id| of |user contexts|: