Order_model.php mis-type

I have no idea what effect this has or hasn't but I stumbled across it in my travels through the Cartthrob  code.

File: /cartthrob/models/order_model.php
Line: 1085
Old: unset($row['exrta']['row_id']);
New: unset($row['extra']['row_id]);
Change: fixed the mis-type of the word "extra"

BTW, if anybody out there has ever written any documentation on the Cartthrob code, I'd sure appreciate a link referral. I've been wandering through it for days accomplishing: 1) revising the layout of the Orders tables in the Order Management pages; 2) increasing my understanding of Php; 3) some amused chuckling at the residual comments (I'll post some later); 4) not much else.