Using Schedule 13 and your examples… everything seems to flow properly.
For year 1 you would enter your 40,000 in box C (Net addition or deduction) of the S13WS
This correctly flows 40,000 to only line 126 of the T2S1.
For year 2 on the S13WS you would enter your 40,000 in box A (Balance at beginning of year) and negative 10,000 in Box C (Net addition or deduction) and it will automatically populate the balance of 30,000 for box D (Balance at end of year).
In this case it will properly show 30,000 on line 126 of the T2S1 and 40,000 on line 414 of the T2S1.