Ariens gt 20 931 series speed

Hello, just got a Ariens GT20,  931 tractor.   So im learning about these. Got it to till a garden.  I would like to get better control on my ground speed / aka SLOWER.   The area that i like the Speed Selector in, is on the edge of the neutral position and even 1/8th inch movement gets to be to fast.  Basically i want a creeper gear setting even if i lose topend speed . I have seen alot of peaple having to slow of speed problems but not to fast. And yes i have tried to reverse the info given to slow me down but....
 
So any ideas ?      Its got to be able to be done in settings i would think?
 
Other than that it runs great!
Thank you