The reflectance coefficients provided in the GeoTiff Header are used as a multiplicative to convert SkySat imagery from Analytic TOA Radiance values to TOA Reflectance.
The order of the reflectance coefficients will go according to the order of the image bands. In SkySatCollect images, the band order is BGRN:
"bands": [1: Blue, 2: Green, 3: Red, 4: Near-infrared]
Likewise, the order of reflectance coefficients will be:
"reflectance_coefficients": [1: Blue, 2: Green, 3: Red, 4: Near-infrared]
For more information about Convert Radiance values to Reflectance please check this document: