Ok, I'm not sure I understand this change thing but I can accept it. Can you explain what the addresses on the left are?
Well they are related to change.
Lets pretend your wallet has only 1 address with value. Address A. Since it is the only address you have used (via generate new address button) it is the only one you see. You have 10 BTC.
So you may think your wallet looks like this:
-----------------------------------
Address A - value 10 BTC.
nothing else
However the wallet pre-generates 100 addresses and puts them in a "key pool"
So your wallet actually looks something like this:
-----------------------------------
Address A - value 10 BTC (visible)
Address B .... Z - value 0 BTC (hidden)
With me so far?
Now say you send/transfer/spend some coins. You send me 4 BTC. You might think it works like this:
Address A - 10 - 4 = 6 BTC
and now your wallet still has only 1 address (address A) and it has 6 BTC.
but it doesn't. Anytime you perform a transaction Bitcoin empties that address (there are uber geek reasons for why).
So it actually works like this:
Bitcoin makes a transaction
FROM Address A (value 10 BTC)
TO Address Me (value 4 BTC)
TO Address B (value 6 BTC)
10 BTC in & 10 BTC out
So after the transaction your wallet looks like this:
-----------------------------------
Address A - 0 BTC (visible)
Address B - 6 BTC (hidden)
Address C to Z - 0 BTC (hidden)
Now imagine you send me another 2 BTC. You might
think it is going to come from Address A right? I mean it is the only address in your wallet you see.
However A has no value. Instead it will be transaction like this:
FROM Address B (value 6 BTC)
TO Address Me (value 2 BTC)
TO Address C (value 4 BTC)
6 BTC In & 6 BTC Out
So after the transaction your wallet looks like this:
-----------------------------------
Address A - 0 BTC (visible)
Address B - 0 BTC (hidden)
Address C - 4 BTC (hidden)
Address D to Z - 0 BTC (hidden)
Now I left a lot out like how keypool constantly "refiils" so you always have 100 "unused" addresses at all times and how Bitcoin tracks not just aggregate value but the prior output but hopefully that makes more sense then getting into the weeds.
TL/DR version:
Your wallet contains more addresses than you think it does because anytime you send coins the "Change" is sent to a new unused address.
There are tools to export your entire wallet and you will see all those "hidden" addresses and what value they have. If you exported your wallet you would find those "unknown" inputs in the transaction above. Also you would find the "unknown" output (it is your newest "change" address).