The audit starts by tying drag, drive, and terminal speed to the same numbers. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Start from the linear drag check
Drag coefficient 3 N*s/m times speed 4 m/s gives 12 N.
3⋅4=12N
The same numbers set terminal speed
Drive 12 N over coefficient 3 N*s/m gives terminal speed 4 m/s.