The statement H(30) = H(25) + 5 means that, "when Amelia was 30 months old, she was 5 centimeters taller than when she was 25 months old"
Given that,
Baby Amelia's parents measure her height every month
It is given that H(t) models Amelia's height (in centimeters) when she was "t" months old
Given statement is H(30) = H(25) + 5
So, we can say that H(30) = Amelia's height when she was 30 months old
H(25) = Amelia's height when she was 25 months old
So H(30) = H(25) + 5 means that,
Height of Amelia when she was 30 months old is 5 centimeter more than Amelia height when she was 25 years old
Or we can say that,
When Amelia was 30 months old, she was 5 centimeters taller than when she was 25 months old