Define "wet" diaper

swith5

I've been wondering this for months, and just haven't asked. When we say "watch LO's diaper output" how wet is considered wet? I change my LO every 2-3 hours and his diaper is usually some amount of wet but I never know if it's wet enough. They seemed fuller when he was younger - is that because the diaper absorbency changed (he's 8 months in pampers size 2) or because he's not getting enough, I don't know. Obviously if I was noticing dry diapers after 2-3 hours I would be concerned, but when should I be concerned about the amount of wet diapers?