To change the shadow size, the parameter must be added to the box-shadow property, specifying the size of the shadow relative to the size of the object.

The answer to the question is spread

To change the shadow size, the spread parameter must be added to the box-shadow property, specifying the size of the shadow relative to the size of the object.

Explanation:

The spread parameter is used to contract or expand a shadow to change the shadow size. To increase the shadow size the radius is set to a positive value while to decrease the size of the shadow, the spread radius is set to a negative value and a zero value will leave the shadow size unchanged

Example

text-shadow: 3px 3px 20x 5px lightblue; color: blue.