Find the value of Δx for which the value of Δy/Δx is within 0.1 units of slope.

Question

Here is the link for the problem that I am trying to solve:

https://ocw.mit.edu/courses/mathematics/18-01sc-single-variable-calculus-fall-2010/1.-differentiation/part-a-definition-and-basic-rules/session-1-introduction-to-derivatives/

The problem is 1c in the pdf:

https://ocw.mit.edu/courses/mathematics/18-01sc-single-variable-calculus-fall-2010/1.-differentiation/part-a-definition-and-basic-rules/session-1-introduction-to-derivatives/MIT18_01SCF10_ex01sol.pdf

The final solution is next:

$$-0.08 \le \Delta x \le 0.10$$

As I understand this is the formula for this problem where m is the slope:

$$-0.1m \le \frac{\Delta y}{\Delta x} \le 0.1m$$

But I can't understand why the numbers on each end are different. Appreciate any help.