Step 1: Divide the number into separate digits:
00940 => 0 0 9 4 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
0 to 0 = 0
0 to 9 = 9
9 to 4 = 5
4 to 0 = 4
0 to 0 = 0
Step 3: Combine the filters to a string:
0 9 5 4 0 = 09540