This is something I don't understand about sunburn - If I'm exposed to 15 minutes straight of sunlight, I will burn, but in 2-5 minute chunks spread out over se

This is something I don't understand about sunburn - If I'm exposed to 15 minutes straight of sunlight, I will burn, but in 2-5 minute chunks spread out over several hours, I can tolerate much more. Is there an equation for this? Like a small coefficient with a high power? 0.1*Te^4 ? Or am I wrong about how sunburn works? This one just shows time as a straight factor, no exponent: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6345802/#:~:text=However%2C%20temperature%20is%20not%20the,3%20s)16%2C17 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6345802/#:~:tex....