bits - Binary Subtraction Borrowing Logic for 1000

i having hardtime understanding borrowing logic 1000 - 0110 . know answer 0010 having trouble understanding borrowing part little.

first step ok 0 - 0 = 0

1000 0110 ----    0

second step 0 - 1 , need borrow . borrow 1 , result 10 - 1 = 1

   ->1     1000     0110     ----       10

but @ next step there nothing borrow, how work ?

when borrow, carry on binary 10 lower bit, so:

  0 ->1  0000  0110  ----     0

then borrow again, , subtract 1 10, 1:

   0 ->11  0000  0110  ----     0

and finally:

   0 ->11  0000  0110  ----  0010

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