The form is calculating a weighted high-albedo area based on the solar reflectance index of the roofing material. So, a low-sloped roof with an SRI value of 100 has a higher weighted area than a roof with an SRI value of 85. Because the required SRI value is 78 for at least 75% of the roof area, if you have SRI value greater than 78 or if you have more than 75% of the roof covered with high-albedo materials, your weighted average can easily be more 100%.