What were the things Via knew and understood because she was Auggie's sister?

From the text:

I've always understood that August is special and has special needs. If I was playing too loudly and he was trying to take a nap, I knew I would have to play something else because he needed his rest after some procedure or other had left him weak and in pain. If I wanted Mom and Dad to watch me play soccer, I knew that nine out of ten times they'd miss it because they were busy shuttling August to speech therapy or physical therapy or a new specialist or a surgery.