Handsome devil huh?
As explained on the updated tables:
When attempting to gain a flank, two actions are involved. First you must check to see if the gladiator is agile enough to make the move by doing a 1d20 check vs Agility (plus modifier). Then to see the LEVEL of success, you must make a 2nd 1d20 check and apply it below.That is, perform an Agility Check and modify it according to the chart. If that succeeds, then you simply make a 1d20 check to see how well you succeeded (and you can actually fail on a 19-20).