The numbers shown by the number line (-2, -1, 0, 1 and 2) are all integers.
Between each pair of numbers, there are 4 equal segments, each one of 1/4 = 0.25 units length. Therefore we can locate, for example, 1.25, 0.5 and -0.75 at the number line.
The question asks for the total bags of dog food. Because they give you two existing values expressing how much dog food of each type there is, all you must do is add them together. 145 + 263 = 408