|x-a| is the distance from x to a, either plus or minus
Now, consider that
|x| = x if x >= 0
|x| = -x if x < 0
and you have
|m - 2.5| <= 0.08
so, if m > 2.5,
m-2.5 <= 0.08
m <= 2.58
Otherwise,
-(m-2.5) <= 0.08
m-2.5 >= 0.08
m >= 2.42
We can write this as
2.5-0.08 <= m <= 2.5+0.08
2.42 <= m <= 2.58