«إجماعهم على أحد أقوال السلف»
Their consensus on one of the earlier Salaf positions.
In the third type, no earlier opinion is found. In the fourth, multiple earlier opinions exist, and later jurists agree on one of them.
For illustration, imagine that two views are reported from early jurists and later qualified jurists uniformly adopt one. That shows the formal distinction; no claim is made that a particular issue has historically met the conditions of consensus.