The first cicuit shows how reset 9 to 1.
The second cicuit shows how change the number "zero" to any other number or letter.
And the third circuit reset F to A.
The numbers connected with the "load" node is indicator of the number displayed than reset:
1=1, 2=2.....9=9, 10=A, 11=B, 12=C, 13=D, 14=E and 15=F
