The credit requirement is to connect 50% of the project lighting load to daylight sensors. This does not mean connecting to 50% of the total number of fixtures, as some fixtures have higher power loads than others. If 30% of fixtures contribute to 60% of your lighting load, then you need fewer sensors to meet the minimum threshold for the credit. Or conversely, by adding more sensors, you can achieve the 75% Exemplary Performance threshold and earn an extra point through IDc1.