Step 1: Divide the number into separate digits:
89970 => 8 9 9 7 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
8 to 9 = 1
9 to 9 = 0
9 to 7 = 2
7 to 0 = 7
0 to 8 = 8
Step 3: Combine the filters to a string:
1 0 2 7 8 = 10278