1. Release thousands
6 - 0 = 6; drop 6.
5 visual steps / borrow-window subtraction
6 - 0 = 6; drop 6.
8 - 5 = 3; drop 3.
Pay right borrow; release 0: 4 - 3 - 1 = 0.
Borrow 10; release 5: 12 - 7 = 5.
Read 6 | 3 | 0 | 5 as 6305; borrow is gone.
A few quick rounds make each dropped digit feel light; borrow is the only thing to keep.
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