Good job posting your specs.
You CAN just edit the PHP file and add those values directly.
You CAN use ADAPT instead of RATIO with drop call percent set to 100% and set the max dial level to literally any value you want. The drop call percent is the limiter (if you never exceed the drop calls, it's going to stay at the max, thus this method is merely a direct entry of the ratio entry when drop call percent is at 100).
You could also actually USE predictive mode if you have 20 or more agents. But don't leave the building with it in predictive mode if you're not familiar with it. Predictive mode uses "available only tally=N" along with one of the ADAPT dial methods and of course you can play with all the other settings in the green section. All of which have a ? help button. Beware changing anything by more than "1", though. For instance: I forbid you to change "Adapt Intensity" by more than 1 per day unless you are prepared to hang your head in shame when it overloads your server but doesn't actually help with dialing. All it does is make the server "calculate more often", which doesn't actually make it dial more or less, just calculate what to dial more often. But many room managers crank that up to 40 More Intense, then call in to find out why their dialer no longer functions. I chuckle, and tell them to stop using adapt cuz they aren't qualified (adapt is not "pedal to the metal", it's "informed decision": If you want to put the hammer down, there are other options that don't involve overloading the server.)