Baby's diaper

Jonah went to visit his friend Kumar who had recently got their first son. He undid the flannel swaddling to better check out the baby and then called out, "Hey Kumar, I think your kid's diaper needs changing!" "Nah, it's okay!" Kumar replies. "I don't think it's okay. He's stinking." "It's fine. Don't worry about it." "It's definitely not fine. Shits spilling out." "It happens, but that's okay." "Please tell me why it's okay." "The box says diaper's good for eight to twelve kilograms."