How does a judge assess a settlement in a civil matter?

As discussed by Belobaba J, in Leslie v. Agnico-Eagle Mines, 2016 ONSC 532, at para. 8, But how does a judge do this? Judges are obviously not in position to second-guess the actual amount of the proposed settlement. Nor should they do so. The most they can do, apart from making sure that the settlement was negotiated at arm’s length by competent counsel, is (1) scrutinize the actual agreement and supporting affidavit material for any so-called “structural” indicators that suggest collusion or conflict of interest and (2) satisfy themselves that the settlement amount falls within a range or zone of reasonableness. [Notes omitted.]