I got confused here, what I should setup in "steps per": 1600 or 32000?

My unit is "inch", if I setup "steps per" to 1600, it means it takes 1600 steps to make one inch movement, right? but in my system, I use 1600 step/rev (200*8 micro-step) motor and 20 tpi (20 threads per inch) rod, so does it mean I should put 32000 in "steps per"?

To imagine, my motor can be set to 125 micro-step with 25000 step/rev, with 20 tpi rod, the number will be 500000 steps per inch, then the maximum velocity will be only 3, which looks weird? So in my real case, 1600 or 32000?

Thanks.