That table must be for all games, Souness had games against Cheltenham, Yeading and Mansfield amongst others. On league games alone, out of our last 4 managers, Roeder (45.51) has the best points percentage, followed by Allardyce (41.27), Keegan (41.18) then Souness (39.77).
Keegan was here for the least number of games so his results would almost certainly have got much better if he'd stayed longer, for instance if he'd stayed and we'd won against Hull his points percentage would have been the second best and only 1% behind Roeder. I would think after another 3 games he would have been the best of the 4.