Step 1: Divide the number into separate digits:
0537 => 0 5 3 7
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
0 to 5 = 5
5 to 3 = 2
3 to 7 = 4
7 to 0 = 7
Step 3: Combine the filters to a string:
5 2 4 7 = 5247