With the same torque, larger inertia changes spin more slowly. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Larger inertia gives a smaller alpha
The same 12 newton meter torque acting on inertia 12 gives alpha 1 per second squared.
α=12/12=1persecondsquared
The torque did not change
Only inertia changed: alpha goes from 2 down to 1.