How many hours ASUS eeepc 1005HA lasts? product says 8.5 battery life?

i just bought this unit, drained the battery and have the initial charging of straight 8 hours followed as instructed. but when its already full charge, i noticed the sudden change of battery meter for using it for 1 hr/.30 mins. The next day i found out the battery meter depleted. what is battery life means? the staff said stand by mode...is he correct? as far as i know its how long the battery can cope up with continuous applications..im only using ym and surf at the same time.. what u think?