Jansport backpack size chart?

i went to jansport.com, and found a backpack i liked, and i wanted to know if it would hold my stuff. The following website tells you what it holds, http://www.jansport.com/size_comparison/js_sizechart_school.html but it was wondering, if it holds all of that at one time, or seperatly. and which capacity... show more i went to jansport.com, and found a backpack i liked, and i wanted to know if it would hold my stuff.
The following website tells you what it holds,
http://www.jansport.com/size_comparison/...
but it was wondering, if it holds all of that at one time, or seperatly. and which capacity should i get,

and do you think i should get a back pack from jansport, or somewhere else. Im going to be in 11th grade, and i have 4 classes a day, alternating the classes everyother day, so 8 total.
Thanks