Using Sumifs To Check Multiple Criteria On The Same Column

[iamhttp]

Hey guys.. I've been talking these pages for a few weeks now and decided to join up

I humbly ask for some minor help in something that i just can't wrap my head around..
the story is this :
I've got two sheets, one is a database type sheet with a bunch of transactions with all their relative information and one is a sheet that tries to summerize the information depending on the criteria you feed it.

sheet 'transactions' holds the database
sheet 'item list' holds the table.
sheet 'information' holds some data for various arrays i use, the most important is an array called all = { jenny, amarr}
(the list is taken from the 'information' sheet)


=SUMIFS(Quantity,Item,item_list,Sold_Bought,D3,mon th,B1,Char,INDIRECT(B2))

this is the formula i have, some basics:
Trying to sum the quantity on these criteria
Item matching the type of item in the list(in 'item list')
Sold_bought and D3 is to check if i bought or sold that item
month and B1 is to sum by a specific month

B2 holds text that's data validated to {jenny, amarr, all}, with jenny = {"jenny"} for example.
so indirect(B2) refers to an array holding the names that i want to summerize by.

this is as far as i got, if i type in Jenny and Amarr in B2, it works fine.
if i type All it doesn't work.
i've read multiple solutions stating that i need to add a sum in the start of things, so i'll have :

=Sum(SUMIFS(Quantity,Item,item_list,Sold_Bought,D3 ,month,B1,Char,INDIRECT(B2)))
but when i hit ctrl+shift+enter i get the same number for each item type.
in this case, i get the number 10,289,272. no clue why!

So my questions are these:

1)What exactly does sumifs do in when checking an array of conditions? does it sum up everything by condition A, and then everything by condition B?(given A and B are in the same column)
2)why doesn't my code work properly?
3)how could i have figured this out alone without bothering you guys?

any help is much appreciated.