here is my (very lame) attempt^* to explain the method by which I (and Nancy) learned to subtract

I’ll use the same sum

34-
17
—-

first, grab (borrow) a 1 from the 10’s column, as you do with the Bess method.

 3¹4-
 1 7
—-
   7

Then, in the tens column, instead of crossing out the 3 and making it a 2 (a la Bess) making the sum 2-1, you “pay back” the 1 you borrowed to the bottom row and add it to the number that is there – so, in this case, you would have 3-2

 3¹4-
₁1 7
—-
 1 7

I hope that makes sense!

^*please be warned that I have difficulties explaining most things in a coherent manner!