Can somebody me understand why the measure of angle a is congruent to 30 degrees but isn’t acute? ?

it’s about negation

Angle A is originally equal to 30 degrees and it is originally acute. When you negate it, you flip what the original statement is saying.

So originally angle A is 30 but now it flips to not being 30
Angle A is originally acute, but it flips to not being acute.

note: "negation" is effectively the same as "opposite"

Another note: those two statements are separate it seems. If you say an angle is not 30 degrees, then there is no way to guarantee it is acute or not acute.