Pointer memory size

when sir declared the pointer variable to the array in the latter half of the video like int*a = new int[5], i have a doubt about the size of a since later he assigned a[0] = 11 and a[1] = 1 but isnt it the fact that a only points to the first element of the array and not every element so how was he able to assign elements using a[0] = 11…/././././././././.