Modify All is the level of access that the sales user will have on the Account object after being assigned to a muting permission set that mutes Delete access on Account. Muting permissions are a way to reduce or remove access to objects or fields for users who are assigned to permission set groups. Muting permissions can only mute object-level permissions, such as Create, Read, Edit, Delete, View All, or Modify All, but not field-level permissions or other permissions. Muting permissions can only reduce or remove access that is granted by other permission sets or permission set groups within the same permission set group, but not by profiles or other sources of access. Therefore, in this case, the muting permission set will only mute the Delete access on Account that is granted by the permission set group, but not the Modify All access that is also granted by the permission set group.