when i go to send a fraction of a coin using my WO wallet on my online machine, i check the "preview transaction" directly above the continue button, and see that its emptying the contents of an entire address housed in that wallet. 

https://en.bitcoin.it/wiki/Transaction#Output

i'm guessing that the tx has to account for the whole wallet in one address in that WO wallet but in actuality only what i want to send is sent and the rest is sent back to me automatically in that wallet. 

is that correct?

thanks.